Lesson video

Hello.

I'm Mr Lund and this lesson is on the order of operations.

Hi everyone, let's calculate four plus five multiplied by two.

Four plus five that's nine multiplied by two that gives me eighteen.

Ooh, hang on, four plus five multiplied by two, well five multiplied by two is 10, four plus 10 gives you 14, I'm confused.

Which part of the calculation should we complete first? We use the order of operations to prevent any confusion.

Here is a diagram showing the order of operations, brackets, indices, multiplication, and division, addition, and subtraction.

Let's identify the operations that we are using in this calculation.

Now rewrite your calculation, underlining the first operation you are going to use.

Let's rewrite our calculation again.

That gives an answer of 14.

So let's start with some quick fire examples.

Calculate four plus five in brackets multiplied by two.

Which part of the calculation should be completed first? Here is our order of operations diagram, very nice.

Let's highlight the operations we're going to use.

And then let's rewrite our so.

underlining the first operation that we're going to use.

And we have brackets that we're going to use and simplify our brackets.

Let's rewrite that as nine multiplied by two gives me an answer of 18.

Here we go.

Calculate six, subtract five plus two.

Which part of calculation should be completed first? Let's have a look at our order of operations diagram.

Now, which operations am I using in this case? Now we are going to read left to right.

So the first thing I need to do is six subtract five, rewrite our calculation and that gives us an answer of three.

Let's move on.

Here we go, six plus five multiplied by negative two.

Which part of the calculation should be completed first? Here is our order of operations diagram.

Hello again, let's highlight the operations we are going to use, and we are reading our calculation from left to right.

And the first thing we are going to do is multiplication.

So let us underline the multiplication of five multiplied by negative two.

We rewrite that as six plus negative 10, and that gives me an answer of negative four.

So it gets a bit trickier when you start adding negative numbers in that as well.

So you got to be comfortable with those.

Well, this looks a bit trickier, but following the order of operations, I think we'll be okay.

Which part of the calculation should be completed first? Look at our order of operations.

Highlight the operations we're going to use, and then follow the system.

Six subtract 56 divided by two or the 56 divided by two is our first calculation.

Let's underline it and then rewrite.

Six subtract 28 is going to give us a negative answer.

Ooh, looks like we got some indices here.

Which part of the calculation should be completed first? This our order of operations.

Highlight the operations you going to use.

Indices, multiplication and division, addition and subtraction.

So we are going to work with two to the power of two first.

Let's underline that and rewrite our calculation 80 minus two, multiplied by four.

Let's underline the multiplication part 80 subtract 8 gives me an answer of 72.

Gets a bit tricky, isn't it? So here are some questions for you to try.

Pause the video and resume once you've finished.

Here is the solutions to question number one.

Did you find Eva's mistake? Let's try question two.

Pause the video to complete your task, and resume once you've finished to check your answers.

Here's the solutions to question number two.

It is a really nice thing to do, if you follow the steps that you've been given.

It does help, underline the operations that you're first going to do, and then rewrite your expressions to find your solutions.

Let us try question number three.

Pause the video and return when you would like to check your answers.

Here's the solutions to question number three.

These are getting a little bit trickier now.

One technique you could use is called trial and improvement.

So to find the missing number, you could just play some of the numbers in, and see around about if you're close to the solution or not.

Another technique you could use is to work backwards.

So we've got eight plus a missing number times by three equals 20 you could think of it almost as an.

Right, you can't think of it as an equation, but you could think of it being an algebraic equation.

Saying instead of the box, you could write a letter X for example, and then that would be eight plus three X equals 20, and then solve from there.

Subtract 8 from both sides, divide both sides by three, and that will find you the missing number.

So a couple of different techniques, for more challenging questions there.

Last question, pause the video and return, when you want to check your answers.

Here's solutions to question number four.

Four different examples that you would have to work through systematically to find the right answer.

How did you do? Oh great, glad you did well.