Lesson video

Hi, I'm Mrs. Wheelhouse, and welcome to our series of lessons on how to use your Casio calculator.

In these lessons, we're looking at three of the Casio calculator models.

So let's get started.

By then end of today's lesson, you'll be able to use the fx-991CW to perform calculations with numbers and solve equations numerically.

On the screen, you can see some of the keywords we're gonna be using in our lesson today.

Feel free to pause the video now and read through these definitions.

Our lesson is broken into three parts.

We're going to begin by looking at conversions.

In this lesson, we'll be using the Casio fx-991CW model.

We will cover how to use this calculator to carry out different calculations.

After switching the calculator on, you will see this screen.

You can use the arrow keys to navigate between the options.

For now, we're going to focus on calculate.

Press the EXE or execute button.

Inputting a mixed number into the calculator and pressing execute returns the same value, but has an improper fraction.

Let's do a quick check.

What does inputting an improper fraction into the calculator and pressing execute return? Pause the video while you work this out now.

Welcome back.

You should have noticed it returns the same improper fraction.

So how can I change between improper fractions and mixed numbers? Well, you need to use the FORMAT button.

When an improper fraction is displayed, you can change the format of the value by pressing the FORMAT button.

The value can be displayed as a decimal, improper fraction, or mixed number.

Let's do a quick check.

Using your calculator, select the correct equivalent decimal form for 1349/52.

Pause the video while you work this out now.

You should have noticed it with C.

Well done.

Is there more that my calculator can convert? Well, yes, Sam points out you can also convert with time.

We can change two hours and 20 minutes into hours.

Pressing the shift button followed by the plus, allows us to write in the form hour, minute, and second.

Pressing the format key allows you to display the time in different ways.

So for example here, two hours and 20 minutes can be expressed as 2.

3 recurring hours, 7/3 of an hour or 2-1/3 hours.

A value in hours can be converted into hours, minutes, and seconds.

Pressing the shift button followed by the plus, converts to the form hour, minute, second.

So 7.

6 hours is equivalent to seven hours, 36 minutes and zero seconds.

Let's do a quick check.

3.

875 hours is equivalent to what time? Pause the video while you work this out now.

Welcome back.

You should have said it's equivalent to three hours, 52 minutes and 30 seconds.

Numbers can be written in prime factor form.

So for example, 49 is equivalent to seven squared and 124 can be expressed as two squared multiplied by 31.

Let's see how the calculator can help us to express numbers in prime factor form.

We enter 360 and press execute.

We then press the format button and move to prime factor.

Pressing execute again will give the number in prime factor form.

So 360 can be expressed as two cubed multiplied by three squared multiplied by five.

Time for a quick check.

Select the missing number here when we're expressing 10,375,750 in prime factor form.

Pause and work this out now.

Welcome back.

The missing exponent was three.

It's now time for your first task.

Question one, convert the following times to hours.

Pause and do this now.

Question two, convert the following number of hours to hours, minutes and seconds.

Pause the video and do this now.

Question three, fill in the gaps please.

Pause the video and do this now.

Welcome back, it's time to go through our answers.

For question one, one hour and 15 minutes is equivalent to 1.

25 hours.

Two hours, 20 minutes, and 20 seconds is equivalent to 2.

338 recurring hours and four hours, 15 minutes and 16 seconds is equivalent to 4.

254 recurring hours.

Well done if you got those all right.

Question two, 7.

25 hours is equivalent to seven hours and 15 minutes.

3.

7 hours is equal to three hours and 42 minutes.

7.

42 hours is equal to seven hours, 25 minutes and 12 seconds and 3.

63 hours is equal to three hours, 37 minutes and 48 seconds.

Well done if you've got those right.

Question three, you had to fill in the gaps.

For A, you should have filled in 11, part B, the matrix when it was two and the missing base was five.

For C, we should have two to the power of seven and three to the power of one, but you may have got those written around in the other order.

So you may have three to the power of one first and then two to the power of seven.

For D, the missing exponent to go with the base of three was three.

And the value represented by the question marks should equal one.

Now this could be done by having a base of one and any exponent, for example, one to the power of 124 would still give you one, or you could have any base, but you'll need an exponent of zero.

So for example, 10 to the power of zero.

That would give us one.

Well done if you got that right.

It's now time for the second part of our lesson.

We're gonna be solving linear equations.

Aisha wants to know what else her calculator can do and Sam points out, "Well, it can actually solve some types of equations." From the home screen, you can navigate to see more options.

We're going to look at both the equation and inequality options.

We're going to start with equation.

Solve the equation 9x subtract seven equals 25.

Aisha says, "Well, I already know how to do this.

The answer will be 3-5/9." Well is Aisha correct? Well, we can check in the following ways.

We can rearrange and solve the equation.

You can also use our calculator.

From the home menu, select equation, and then navigate to solver.

To input the equation, we use the X button to represent the variable and the equal sign that is above the left parenthesis.

Press execute, then navigate to the execute option and press the execute button again.

The value for the variable is now displayed.

This mode can be used to solve linear equations with one variable.

Let's do a quick check.

The solver mode can solve this equation without the need for rearrangement.

Is that true or false? And don't forget to justify your answer.

Pause the video and have a go at this now.

Welcome back.

You should have said that it's true.

You can try this out for yourself.

You should find that X is equal to eight.

The solver mode can solve this equation without the need for rearrangement.

Four equals 5y plus 19.

Is that true or false? And don't forget to justify your answer.

Pause the video and do this now.

Welcome back.

You should have said that's true.

And again, you can try this out for yourself.

You will need to type X instead of Y into your calculator, and you should find that Y is equal to negative three.

Our calculator can also solve pairs of linear simultaneous equations.

From the high menu, select Equation, and then navigate to Simul Equation, which stands for simultaneous equation.

And then select 2 Unknowns.

Your calculator will only accept equations in the form axe plus by equal c.

So it may be necessary to rearrange before inputting.

So the equation w plus h plus 8 equals zero can be rearranged to give us x plus y equals negative 8.

And h equals 4W minus 17 is rearranged to give 4x subtract y equals 17.

Now you might be saying, "Hang on a second, how come we've got w and h on one side, but x and y on the other?" That doesn't happen when we rearrange.

Now because the calculator uses x and y, it's important that you know what variable x is representing and which variable y is representing.

So in this case, I've got x representing w and y representing h.

I then enter the coefficients into the calculator.

I need to be careful with any negative values.

Pressing execute gives one value and then pressing execute again shows the second value.

We can interpret this as w equals 1.

8 or nine over five and h is equal to negative 9.

8 or negative 49 over five.

Still quick check.

You can enter any pair of simultaneous equations into your calculator without needing to rearrange.

Is that true or false? And don't forget to justify your answer.

Welcome back.

You should have said that it's false.

Remember, equations need to be in the form axe plus by equal to c.

So it may be necessary to rearrange first.

Time for your second task.

For question one, solve the following without using a calculator and then check your answers using the calculator.

Which way of solving is faster? Pause the video and work on this now.

Question two, solve the following pairs of simultaneous equations using your calculator.

Pause and do this now.

Welcome back.

Time to go through the answers.

For question one A should have x is 36, for B, x is two, and for c, y is equal to negative 59/17.

For question two, you can see our answers displayed here on the screen.

I've given them both as improper fractions and as mixed numbers.

Well done if you've got this right.

Time for the third part of our lesson today.

And that's on solving polynomials.

"So my calculator can solve linear equations including simultaneous ones.

Anything else it can do?" Well, it can solve polynomial equations.

It can also solve quadratic inequalities.

From the home menu, select Equation and then navigate and select Polynomial.

Choose the general form for the polynomial you want to solve.

So you can see we have quadratic form at the top here.

Let's solve two x squared plus nine x plus four equals zero.

So in this mode we need to enter the coefficients or the constant term.

And remember, our calculator only accepts equations in the form axe squared plus bx plus c equal zero.

So you may need to rearrange first.

When you're ready, press execute to solve and then press execute again to see the second solution.

So the first solution is x is equal to negative half and the second x is equal to negative four.

Time for a quick check, use your calculator to find the solutions or solution to x squared plus 8x subtract 20 equals zero.

Pause and do this now.

Welcome back.

When we enter this into our calculator, we find two solutions, x equals two and x equals negative 10.

Let's try solving x squared plus 8x - 20 is less than zero.

Aisha says, "Well, I'll use my calculator to find the roots," which we just saw quite quick to do, "And then work out which way round the inequality sign should be." And Sam says, "Well, you could do that or.

." From the home menu, select Inequality and then choose the general form for the polynomial you want to solve.

Make sure you choose the correct inequality.

So here we want our quadratic to be less than zero.

So we need to choose the strictly less than zero option.

So let's do this now please.

Using that option, find the solutions to x squared plus 8x subtract 20 is less than zero.

Pause and do this now.

When you enter these values with a calculator and press execute, you find that x's lie between negative 10 and two.

Well done if you got that right.

It's time for our final task.

Question one, solve these quadratic inequalities to two decimal places if appropriate.

Pause the video and work this out now.

Welcome back, you can see the answers displayed on the screen now.

Feel free to pause so that you can check your work.

It's time to sum up what we've looked at today.

Some calculators can perform more than just basic calculations.

The fx-991CW could convert between different formats of values and it can also solve equations numerically.

Well done.

You've worked really well today.

I look forward to seeing you for more math in the future.

Goodbye for now.