Lesson video

- Hello, and welcome to this lesson today on energy in the home.

My name is Mrs. Robinson, and I will be going through this lesson with you.

You will need a calculator for this lesson, so if you don't have one handy, then pause the video here and go and grab one now.

So lesson title today is Energy in the Home, and your outcome is to make calculations on energy use in the home and the cost of energy.

The keywords today we will be using are power, which is the rate at which energy is transferred.

We had that from last lesson.

Electricity is the flow of electrical power, and watts is a unit of power.

Our lesson outline today for energy in the home will be converting units of time, calculating energy in kilowatt hours, cost of energy, and energy bills.

So we're gonna start off with converting units of time.

So our first bit is converting units of time, and we're gonna start by converting hours into minutes.

So you need to know that one hour is equal to 60 minutes.

And we can write hour as the letter h.

It's got to be lowercase.

And minutes, we can do a shorter version of mins.

So one hour, if we were to convert that into minutes, we multiply it by 60.

So that gives us the 60 minutes.

If I had three hours, then what I'm looking to do is I will take that three hours, and then I will multiply it by 60, and then that would give me 180 minutes.

So let's have a little go at some practise questions.

So watch me do this one first, and then we'll go through the next one together.

So we're gonna convert six hours into minutes.

So you just need to remember that one hour is 60 minutes.

So for six hours, we're gonna do 6 multiplied by 60, which will give us 360 minutes.

And then, for the one that we're gonna do together, you're gonna convert nine hours into minutes.

So have a little think, how many minutes are in one hour? We should be thinking one hour is 60 minutes.

We've got nine hours to convert to minutes.

So, what are we gonna do? That's right, so we're gonna do 9 multiplied by 60.

Put that into your calculator, and then you'd get 540 minutes.

Well done if you've got that.

So now, you're gonna have a little go at some questions yourself, just make sure you've got your calculator handy.

So this one, two hours is equal to how many minutes? Is it 200, 120, or 1,200? Okay, so hopefully, you've got an answer, and your answer should have been 120.

We're doing 2 multiplied by 60.

You get 120 minutes.

So now, we're gonna look at converting between minutes and hours this time.

So, same idea as before, we've got 60 minutes in an hour.

So before, we were multiplying by 60 to go from hours to minutes, but this time, we're going from minutes to hours, so we're gonna divide by 60.

So if we had 120 minutes, then we would do 120 divided by 60, which would then give me two hours.

So now, we're gonna have a little bit of a practise.

So if I had to convert 360 minutes into hours, then I've just got to remember that 60 minutes is in an hour, and then I would need to do 360 divided by 60, put in my calculator, then I would get six hours.

So let's do one together.

So if I had 720 minutes to convert to hours, what have I got to remember first? I've got to remember that there are 60 minutes in an hour, and then I'm gonna take my 720 seconds and then divide that by 60.

You pop that into your calculator, and then you should get an answer of 12 hours.

So well done if you managed to work through that with me.

Okay, so now you can do a little quick check.

So if I've got 480 minutes, is that equal to how many hours? Is it four, six, or eight? Okay, so hopefully, you've had a little go at that, and we should have got an answer of eight hours.

We've done 480 divided by 60 to get the eight hours.

So well done if you've got that.

So another quick check.

So, 540 minutes is equal to how many hours? Is it 9, 5, or 12? Okay, so hopefully, you've had a little go at that.

So you should have got an answer of nine hours.

So you do 540 divided by 60 to give you the nine hours.

Okay, so now you're gonna have a little go on your worksheet for task one, converting units of time.

So pause the video here and then play again when you are ready to move on.

Now, we're gonna go through the answers.

So part a was to about the following from minutes to hours.

So in order to do that, you would take your time in minutes and then divide by 60.

So for part one, you should have got one hour, part two would be 0.

9 hours, and then part three would be 1.

35 hours.

So just be careful with your decimal points and that you've not forgotten that for those times.

For part b, you had to convert the following from hours to minutes.

So in order to do that, you'd have to multiply by 60.

So for part one, you would get 240 minutes, for part two, you'd get 960 minutes, and then, for part three, you should get 135.

Each of those, you had to multiply by 60.

So for part c, this was a little bit trickier, but hopefully you've managed to figure it out.

So a runner takes 2 hours and 15 minutes to run a half marathon.

So you first had to convert the time into minutes.

So you'll notice already you've got the 15 minutes there, but you have to convert that two hours into minutes as well.

So to do that, you would multiply by 60 and do 2 multiplied by 60, which would give you 120, but then you have to add on those 15 minutes as well.

So you should get a final answer of 135 minutes.

For part two, you had to convert the time to hours.

So you've got two hours, which is already in hours, so you don't need to do anything there, but you've got that extra 15 minutes to convert to hours.

So just remember, you would divide by 60.

15 divided by 60 gives you 0.

25, and then you would add on the two hours that you had originally.

So you should get a final answer of 2.

25 hours.

So well done, especially that last one if you've got it, 'cause that was a little bit trickier for you.

So now, we're gonna move on to energy in kilowatt hours.

So we've already done, in the last lesson, we were calculating energy in terms of joules, but this time, we're using some different units, so we have to do things a little bit differently.

So we're now gonna calculate energy in terms of kilowatt hours.

So before in last lesson, we were looking at energy in terms of joules.

For this time, using the same equation, but the units are a little bit different.

So we have energy is equal to power multiplied by time.

But this time, your energy is gonna be measured in kilowatt hours.

That's where we've got the kWh.

That W has got to be a higher case, gotta be a capital letter, okay? And the k and the h have got to be a lowercase letter.

And then we've got power, which is measured in kilowatt, and then your time's gonna be in hours, okay? So just similar to what you've done last lesson in terms of the equation work, but just slightly different units that we've got to use.

Now, you might be thinking, why do we use kilowatt hours for energy instead of joules? Why are we doing this? So just something for you to have a little think on.

Why is it better to have energy in terms of kilowatt hours instead of joules? So I'll give you a little bit of a clue here.

So we've got here written that 50 kilowatt hours is 180 million joules.

So have a little think about it.

You can pause the video here, then play again when you're ready.

Okay, so hopefully, you've had a little think about that, and you've come up with an answer.

So the reason that we use kilowatt hours is, hopefully you've noticed, is that the number that we've got there is a lot smaller, okay? So 50 compared to 180 million.

So it's a bit easier for us to kind of count how much energy we use using those smaller kind of units in kilowatt hours instead of saying 180 million joules.

'Cause otherwise, we're gonna get very, very big numbers that we have to use.

So just means it's just a little bit easier for us to work out our energy bills.

So we're coming to that later on in the lesson.

So we're gonna do a little bit of practise with that energy equation with those different units.

So we've got calculate the energy of that 0.

16 kilowatt guitar which is played for two hours.

So we've gotta think about the equation that we're using.

So it's energy is power multiplied by time.

You can write it in short format if you like using the symbols that we have for energy, power, and time, which is E equals P t.

And then we substitute our numbers in.

So for power, we've got 0.

16 multiplied by time of two hours.

You put that into your calculator, and then you should get an answer of 0.

32, and then put our new units at the end there, so kilowatt hours.

So you're gonna have a little go with me with this next one.

So we've got calculate the energy for a 2.

2 kilowatt oven which is on for three hours.

So, what do you think we're gonna start off with? We're gonna start by writing down the equation first.

That's right.

Energy is power multiplied by time, or you could write E equals P t.

What's the next step? Well, we've got to now substitute our numbers in.

So we've got power is 2.

2, and we have the time as 3.

So it'll be 2.

2 multiplied by 3.

Then you place that into your calculator, and you should get an answer of 6.

6.

And don't forget your units, so that's kilowatt hours, and that's your final answer.

So well done if you've managed to follow along with that.

So now, we're gonna do a quick check question.

So a 0.

1 kilowatt bulb left on for 19 hours uses how much kilowatt hours of energy? Is it 19, 190, or 1.

9? So pause the video here and then play again when you're ready.

Okay, so for this question, you've got 0.

1, which was in kilowatts, and you've got the 19 hours.

So you should have done 0.

1 multiplied by 19 to give you 1.

9.

So I hope that you've got that correct.

So now, you're gonna have a little go at task two on your worksheet.

Pause the video here and then play again when you're ready.

Okay, so I hope you had a good go at those questions.

We're just gonna go through the answers for those just now.

So you had to calculate the energy used in kilowatt hours for the following.

So you had part one was an object has a power of five kilowatts and is on for three hours.

So all you need to do is to multiply your five kilowatts by the three hours.

So you should have got an answer of 15 kilowatt hours for that one.

And for part two, an object has a power of 1,200 watts and is on for 30 minutes.

So hopefully, you realised that power isn't in kilowatts there and your time isn't in hours.

So you're gonna have to convert those first before you use them in your equation.

So to get power in terms of kilowatts, you'd have to divide your 1,200 by 1,000, which will give you 1.

2 kilowatts.

And for your time, you'd convert that into hours by doing 30 divided by 60.

So that would give you 0.

5 hours.

And then you would multiply your 1.

2 kilowatts by 0.

5 hours.

That then would give you 0.

6 kilowatt hours, okay? So hopefully, you've done well in those questions.

Okay, so now you can have a go at part b of task two.

So you have three items, and you need to work out the energy for each of those in those given times.

Pause the video here and start again when you're ready.

Okay, so hopefully, you've done well with those.

We'll just go through the answers for each of those items. So for the hand dryer, you had a power of 1.

7 kilowatts and a time of three minutes.

So you might have to do something with that time so you can work out which one uses the most power.

So hopefully, you've realised you would need to do 3 divided by 60 in order to put that into hours first.

So if you put that in your calculator, you should've got an answer of 0.

05.

And then you'll do 0.

05 multiplied by your 1.

7.

So that should give you an answer of 0.

085 kilowatt hours.

For the drill, similar thing again with the time there.

You would need to calculate that and convert that into hours.

So your 15 minutes, you would divide that by 60, which would give you 0.

25, and then you would multiply your time in hours by the 1.

1 kilowatts that you have there.

So it'll be 1.

1 multiplied by 0.

25, which then should give you an answer 0.

275 kilowatt hours.

And for your tumble dryer, don't need to do any sort of conversions here.

So it'll be just 0.

8 multiplied by 1 just to give you 0.

8 kilowatt hours.

Well done if you've got all those right.

Don't worry if you haven't, if you just forgot to convert those times into hours, but well done if you did get that.

And then, from your answers there, you would then be able to state that the tumble dryer uses the most energy in the given time.

So we're just gonna go to next learning cycle.

So that will be the cost of energy.

So can be calculated using the following formula.

So the total cost is equal to energy used multiplied by the cost per kilowatt hour.

So your total cost would normally come out as pence, and then your energy used has to be in kilowatt hours, and then your cost per kilowatt would normally be given in pence as well.

So if you're given a cost per kilowatt hour in pence, then your total cost, as your final answer, that will also be in pence as well.

However, if your cost is greater than 100 pence, or 100 pennies, we would divide that by 100 to then convert it into pounds.

So it's something a little bit easier for us.

So for example, if I had 174 pence, I would do 174 divided by 100, so that would give me £1.

74.

So now, we're gonna go through some questions.

So follow the first one with me.

A tumble dryer uses four kilowatt hours of energy at a cost of 29 pence per kilowatt hour.

How much does the electricity cost? So the first thing we're going to write down is the equation that we are going to use, which will be total cost equals energy used multiplied by cost per kilowatt hour.

So the numbers we'll take out of the question would be the 4 and the 29 pence.

So this would be, in our equation, 4 multiplied by 29.

You can then put this into your calculator, so you'd get 116 pence.

Now, just remember, if I said it was over 100 pence, we'd usually convert this into pounds.

So we've got to divide that by 100, which would then give me £1.

16.

Now, let's have a little go at the we do.

So your question is, an oven use four kilowatt hours of energy at a cost of 35 pence per kilowatt hour.

How much does the electricity cost? So I'm hoping that you're thinking already, well, I need to write that equation down first.

The one that I'm going to use.

So total cost is equal to energy used multiplied by cost per kilowatt hour.

So, what's next? So next thing is to place my numbers into the equation.

So my energy used is the four kilowatt hour of energy, and my cost is 35 pence per kilowatt.

So that will be, my total cost would equal 4 multiplied by 35, which would give me 140 pence.

Now, I'm hoping that you're thinking, well, that's more than 100 pence, so we want to divide that by 100 to put it into pounds.

So then that would give me £1.

40.

Well done if you've managed to follow through that.

Fantastic work.

So now, we're just gonna do a quick check to make sure that you've got that.

So a games console uses 1.

5 kilowatt hour at a cost of 34 pence per kilowatt hour.

Calculate the cost of the electricity.

Is it, A, 22.

7 pence, B, 51 pence, or C, 0.

04 pence? Pause the video here and then play again when you are ready.

Okay, so I hope you got the right answer there.

So we should have got an answer of 51 pence.

So that would be 1.

5 multiplied by 34.

And because it's not more than 100, we've kept it at 51 pence.

So well done if you've got that.

So now, what you're gonna do is you're gonna do task three on your worksheet.

You have a, b, and c there to have a little go at.

Pause the video here and then resume when you are ready.

Okay, let's go through the answers.

So for the part a, you had a washing machine that used 20 kilowatts of energy, and electricity costs 32.

5 pence per kilowatt hour.

So you had to calculate how much the electricity costs.

So for that one, you would be multiplying 20 by 32.

5, and you would've got an answer of 650 pence, but then you would've divided this by 100 to get £6.

50.

Well done if you got that one.

So for part b, you had to calculate how much the electricity costs for an oven that used 200 kilowatt hours of energy at a cost 28 pence per kilowatt.

So similar to the question before, you would do 200 multiplied by 28 pence.

That's gonna give you an answer more than 100.

So it gives you 5,600 pence.

So you would just divide that by 100, which would give you £56.

So for part c, your question was, at a cost of 33 pence per kilowatt hour, what is the cost of electricity for a hair dryer using 1.

8 kilowatt hours of energy? For this one, similar to what you've had before, you do 33 pence multiplied by 1.

8, so then that would give you 59.

4 pence.

So well done if you've got all those.

So for task three, part d, you've got a table to complete.

So part one is to calculate the energy used by each device, part two is to calculate the cost for each device with a cost of 36 pence per kilowatt hour, and then part three is to convert any cost to pounds, if relevant.

So pause the video here and then continue when you are ready.

Okay, so now we're gonna go through the answers.

So for the energy for the TV, we had a power of 110 and a time of 0.

5.

So you're looking to multiply those two together to get your total energy, so you should've got 55.

For your games console, you're multiplying 50 by 1, so you should get an answer of 50.

And for the bulb, you're multiplying 0.

04 by 5 to give you 0.

2.

So that's part one completed.

For part two, to work out your cost, you would use your energy that you had for each device and then multiply it by 36 pence, your cost per kilowatt hour.

So for the TV, you'd do 55 multiplied by 36 pence, so that would give you 1,980.

For the games console, you would do 50 multiplied by 36.

That would give you 1,800.

And for the bulb, you would do 0.

2 multiplied by 36 pence.

So that would give you 7.

2.

And then, for part three, you had to convert any cost to pounds, if relevant.

So that meant if there were any that were over 100, we want to convert those into pounds.

We want to do that for the TV and the games console.

For the bulb, we would just leave it as 7.

2 pence.

For the TV, it would be a final answer of 19.

80, so £19.

80 for the cost in pounds, and then, for the games console, you should get a final answer of 18 pounds for that.

So again, well done if you've managed to get all of those.

Okay, so part e, similar idea to what we've kind of been doing before, but I want you to think about how much you use a TV, a mobile phone, or a games console.

So if you happen to not use any of these devices, then just take a time for two hours, but if you use it more, for example, the TV you might watch three hours per day, or two and a half hours, that'd be 2.

5 hours.

Your mobile phone, you might be on that for a couple hours a day or maybe more, who knows? So you need to think about what you use for each of these devices.

Once you've put that in, then you can work out what the total cost per day would be, assuming that the cost of energy is 34 pence per kilowatt hour, and then you can work it out per week.

So just think about, well, how many days are there in a week? So once you've got your cost per day, you can work that total cost per week out as well.

And once you've done all that, I want you to think about why this is not accurate over the whole week.

So pause the video here and then continue when you are ready.

Okay, so let's go through the answers now.

The answers that I'll have here are based on a daily use of two hours for each of these items. So if yours is more or less than these numbers, it'll be a little bit different.

But I'll go through the method, so then you can check the sums that you did.

So to work out a total cost per day, we'll first have to work out the total energy that your item has used.

So you've got your power in kilowatts.

You've got your time in hours.

So you'd multiply those together in order to get your energy in kilowatt hours.

So that's your first little bit.

So with the TV, I would do 0.

5 multiplied by 2, which would give me 1 kilowatt hour.

But I'm not quite finished working out the total cost yet.

I would also then need to multiply that by 34 to give me the cost.

So that would give me 34 pence for the TV.

Would be the same idea for the other two as well.

So if you've used two hours for the other two as well, then the answers are there.

So for the mobile phone, I would've done 0.

15 multiplied by 2, which would've given me 0.

3 in my calculator, and then I would've multiplied that by 34 pence, my total cost per day.

And then, for the games console, it would've been 0.

9 multiplied by 2, which would be 1.

8, which is my total energy, and then I would multiply that by 34 pence to get 61.

2 pence.

So that would be my total cost per day.

And then, to get a total cost per week, I just have to multiply the total cost per day by seven because there are seven days in a week.

So if I do that, I get those answers below.

Hopefully, you've had a good think about why this is not accurate over the whole week.

Well, you might be thinking, well, on Mondays, I might be busy doing something else, so I'm not necessarily watching as much TV, or because you're at school through the day, then I don't use my mobile phone as much in those days as I might do at the weekend, so things like that that might affect your time.

So a model answer would be this cost would not be accurate as I use it a different number of hours each day.

If you have something like that, then well done for figuring that out.

So now, we've got the next two parts.

So we've got f and g for task three.

So pause the video here and then play again when you are ready.

Okay, so let's go through the answers for these.

So for f, a fridge has a power of 0.

8 kilowatts and was on for five hours.

The cost of electricity is 44.

5 pence per kilowatt hour.

How much did this electricity cost? So you'll need to work out how much energy in kilowatt hours first that you've used before you can work out the cost.

So you would do 0.

8 multiplied by 5.

So that would give you four kilowatt hours.

That four kilowatt hours, you would then multiply by 44.

5 pence, which would give you an answer of 178 pence.

But remember, you want to convert that into pounds, so then you would divide by 100 to get £1.

78.

For g, you have a 1,200-watt washing machine was on for 1 hour and 45 minutes.

The cost of electricity is 35 pence per kilowatt hour.

How much did it cost to run the machine? So hopefully, you've noticed that the power isn't in kilowatts.

It's in watts, so we need to convert that.

And the time isn't just in hours.

It's in hours and minutes, so we also need to convert that before we can calculate the energy and then calculate the cost.

So you need to do 1,200 divided by 1,000.

That would give you 1.

2 kilowatts.

For your time, you would take your 45 minutes and divide it by 60, which gives you 0.

75.

But then we needed to add on that hour, so our time will be 1.

75.

And then you're gonna do 1.

75 multiplied by 1.

2.

So 1.

75 is your time in hours, and then 1.

2 was your power in kilowatt.

Multiply those together to get an answer of 2.

1.

So that's your energy in kilowatt hours.

You should have got 2.

1.

But we're not quite finished yet.

So then you just need to multiply that by 35 pence.

Then you should get an answer of 73.

5 pence for that one.

So well done if you've had a good go at those questions.

They were very tricky those, but I hope that you got there and me going through it's kinda helped you see what you need to do if you didn't quite get that.

Okay, so we're gonna go through the next part.

We're gonna go through energy bills.

So it's about how you might calculate those.

So using what we've learnt from the previous learning cycles, we can calculate the cost of electricity at home.

So here's an example statement of a bill that you might receive.

So you've got the previous reading on there.

You've got the current reading that you have.

You work out the units used.

So that's just the difference between previous reading and current reading.

You've got your cost per kilowatt hour, so how much it is, and then your total cost.

We've done lots of these bits throughout the previous learning cycles, and we're just putting it together here.

So now, we're gonna go through some practise examples.

So the first example, the previous reading was 59,872 kilowatt hours, the current reading is 60,272 kilowatt hours, and the cost per kilowatt hour is 28 pence.

So we're gonna have two stages to calculate our total cost for what we have used.

We'll first need to work out the difference between the current reading and the previous reading.

So to do this, we'd do total kilowatt hour used is equal to current reading, subtract the previous reading.

So that would be our 60,252 subtract 59,872.

So that would give us a final answer of 380 kilowatt hours.

So that's how much we have used.

So now, we'd need to work out how much that costs.

So we know our cost per kilowatt hour is 28 pence.

The equation is gonna be, total cost is equal to total kilowatt hours used multiplied by cost.

So that'll be 380 multiplied by 28.

We put that into our calculator.

So we get an answer of 10,640 pence.

Now, we're not quite finished yet 'cause we'd like to put this into pounds.

So remember, to do that, we divide by 100.

So we get a final answer of £106.

40.

So now, we're gonna do one together.

So you have a previous reading of 15,672 kilowatt hours.

Your current reading is 15,920.

This time, the cost per kilowatt hour is 30 pence.

So think about what step you need to do first.

So first, we'll need to put the equation down to work out the total kilowatt hours used.

So that's equal to the current reading subtract the previous reading.

So you'd have 15,920 subtract 15,672.

Put that into your calculator, then you get an answer of 248 kilowatt hours.

So that's how many kilowatt hours we have used.

But we're not quite finished yet 'cause we need to work out the total cost.

So, how are we gonna do that? Yes, you're right.

You're gonna start by writing down the equation.

Total cost is equal to your total kilowatt hours used multiplied by cost.

Put your numbers in.

So you should have 248 multiplied by 30.

Put that into your calculator, and then you should get a final answer of 7,440 pence.

But is that my final answer? I hope you say no.

So you need to divide that by 100, and that would give me it in pounds.

So it'll be £74.

40.

So well done if you've managed to follow through on that.

So now, we're gonna do a quick check.

The current reading is 78,523, and the previous reading was 77,489.

Calculate the total cost of electricity at a rate of 32.

5 pence per kilowatt hour.

So pause the video here and then resume when you are ready.

So we'll go through the answer now.

So hopefully, you've noticed that you had to work out what your total kilowatt hours used was first.

So you'll take your current reading and subtract your previous reading.

It'll be 78,523 subtract 77,489.

So you should have got an answer of 1,034 for that.

And then we need to do the next step.

We need to work out the cost.

So that'll be your kilowatt hours used multiplied by your cost per kilowatt hour.

So that'll be 1,034 multiplied by 32.

5.

Once we've done that multiplication, we would've got an answer of 33,605.

And that's more than 100, isn't it? So we'd have to divide that by 100 to get our answer into pounds.

So we should've got a final answer of £336.

05.

So that would've been B.

So well done if you got that.

It is quite a long, tricky question that, but well done for having a go.

So now, you can have a go at task four, part a on your worksheet.

So just watch out.

There's lots of information on there, and you've got two months of bill statements.

You've got September then October.

Pause the video here, then resume when you are ready.

Okay, so let's go through the answers.

So you'd have to first work out September.

So the units used would be the difference between your current reading and your previous reading.

You've done 14,165 subtract 13,780.

Give you an answer of 385.

Then, to work out your total cost, you'll multiply your 385 by 34 pence.

You are gonna have a number much bigger than 100, so remember to divide that by 100.

Total cost would be £130.

90.

Well done if you've got that.

Let's look at the October statement.

So it says that you need to have your previous reading.

So you would take that from your September statement.

Now, your previous reading on your September statement isn't the same as the previous reading on October statement.

So the previous reading on October statement would actually have been the current reading from the September statement.

So hopefully, you've noticed that.

You should have 14,165 there.

Don't worry if you didn't quite get that.

As long as you've done the rest correctly for your method, then well done.

Next step for the October statement is to do the difference between the current reading and the previous reading.

So it'll be 14,923 subtract 14,165.

You should get an answer of 758.

Next thing to do is we have got to multiply our units used by the cost per kilowatt hour to get our total cost.

So it'll be 758 multiplied by 36 pence.

That would give me an answer much larger than 100, so I just need to remember to also divide that by 100 to get it from pence into pounds.

So my final answer will be £272.

88.

So well done if you had a good go at those.

That's a really tricky question to do.

Now, you're gonna have a go at b and c on task four.

So pause the video here and then resume when you are ready.

So let's go through the answers for that.

So Jane received her electricity bill.

The reading on her previous bill was 25,670 kilowatt hours.

The reading on her new bill was 33,250 kilowatt hours.

Cost per kilowatt hour is 27.

5 pence.

Calculate the total cost of her electricity bill.

So first thing we'd have to do for this one is to work out the difference between the current reading and the previous reading.

So remember you're doing current reading subtract previous reading.

So it'll be 33,250 subtract 25,670.

So you should've got an answer, 7,580 kilowatt hours, how many kilowatts we've used.

Then we're gonna work out the cost.

So you would take your 7,580 and multiply that by the 27.

5 pence.

And you'll realise that's over 100, so you would need to divide by 100 to get it into pounds.

So your final answer for that one should've been £2,084.

15.

So well done if you've got that.

Good job.

So for part c, in February, Tom's current reading was 54,821 and his previous reading was 54,402.

February was charged at 25 pence per kilowatt hour.

In July, Tom used 262 kilowatt hours at a cost of 35 pence per kilowatt hour.

Which month did Tom pay more for electricity? So you're gonna have to do a few different calculations here.

So first thing, for February, you need to work out the difference between your current reading and your previous reading.

So you do 54,821 subtract 54,402.

So for that, you should get an answer of 419 kilowatt hours.

So that's how many Tom used in February.

But that was charged at 25 pence per kilowatt hour.

So to do your cost there, you'd do 419 multiplied by 25.

Then that would give you an answer which is greater than 100, so then you'd need to divide that by 100.

So you get a final answer of £104.

75.

For July, you've already got the total number of kilowatt hours used, so that's 262, so you just need to multiply that by 35 pence.

Your answer will be bigger than 100, so you just need to divide that by 100, and you should get an answer of £91.

70 for July.

So these are the prices you should've got for February and July.

Now, we just need to finish with a statement.

Which month did Tom pay more for electricity? You would say, well, Tom paid more in February for his electricity.

So well done if you've managed to get that.

So now, we'll do a quick summary of the lesson.

So just remember, there are 60 minutes in an hour.

Kilowatt hours is used as a unit of energy.

Power can use units in kilowatts.

Energy is equal to power multiplied by time.

You've got the short form there.

It's E equals P t for that.

And total cost is equal to your energy used multiplied by cost per kilowatt hour.

And just remember, energy used there has to be in kilowatt hours.

So thank you for watching that video today.

I hope you enjoyed the lesson.

Please have a go at the exit quiz.

Goodbye.