Video: GCSE Mathematics Foundation Tier Pack 2 • Paper 2 • Question 25

GCSE Mathematics Foundation Tier Pack 2 • Paper 2 • Question 25

02:20

Video Transcript

Evaluate the expression. Write down all of the figures on the calculator display.

Now most scientific calculators will allow us to type this exact calculation in and will apply the order of operations BIDMAS or BODMAS to calculate the answer. There are a couple of little quirks to be aware of though. To get the square root symbol, we press this button. Once we’ve then typed 24.12 multiplied by three, we need to press right on the arrow button. That will take us outside of the square root sign, and we’ll be able to carry on the calculation as normal.

If we type this exact calculation in, we get negative 2.198114554. However, we should always write down in between steps to ensure that we don’t lose all the marks should we accidentally type it wrong.

The first thing we should do is work out the value of the expression inside the square root symbol. 24.12 multiplied by three gives us 72.36. The square root of 72.36 is 8.5064, and so on. It is important that we use this exact number in any future calculations. If we decided to round at this point and you say 8.5 in our next step, we could lose some accuracy. Many calculators have a previous answer button that will allow us to carry this exact number through your calculation.

Next, we should evaluate the expression inside our brackets on the denominator of the fraction. 0.29 minus 1.86 is negative 1.57, and negative 1.57 cubed is negative 3.869893 exactly. Our final step is to divide the unrounded version of the square root of 72.36 by negative 3.869893. And that gives us negative 2.198114554.

Now a common mistake is not to read the question fully. It is telling us to write all the digits on our calculator display. So that’s exactly what we should do. The answer is negative 2.198114554.

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