Nine ways to revise for the GCSE Calculator paper

A student asks:

Hi, I am struggling with trying to revise for my GCSE maths calculator mock… I was wondering if you could give a few tips on how to revise for this exam in particular.

There's a commonly-held belief that the calculator paper is easier than the non-calc one, but I'm not sure I buy it: the calculator just means you can do more difficult maths without having to worry about the arithmetic so much. There are a few places I've noticed students dropping marks they ought to be getting, though, so here are a few things to look out for.

1. Give them what they want

As the old joke asks, what do you call a gorilla with a machine gun? "Sir." Examiners, without wanting to be mean to them, are gorillas with machine guns. If they ask you for an answer correct to three decimal places, give them an answer correct to three decimal places (and round carefully). If they ask you to give a reason for your answer, give them a clear reason. They actually want to give you marks (rather than shoot you), so give them every chance to.

2. Estimate first

Any time you use the calculator, it's worth having a little think about what you expect the answer to be. If you've got a triangle, think about what you expect the missing side to be. Longer or shorter than any of the sides you've got? Similar? What's its area going to be? The more you get into the habit of eyeballing your answers (and giving yourself a little pat on the back when you're more or less right), the better you're going to be able to spot - and correct - wrong answers.

3. Speaking of triangles...

Make sure your calculator is in degree mode - the GCSE is no place for grown-up units of angle like radians. You also want to be clear in your mind about when to use $\sin$ and its friends (when you have an angle) as opposed to $\sin^{-1}$ (when you want an angle.

4. Show your working

It's tempting to look at a question, push a few buttons, and write down the answer. That's not a good strategy: if you make a mistake, you'll lose all of the marks for the question. Maths isn't just about getting the right answer, it's about explaining how you got there. I know, it's tedious to write down every dreary step you've taken, every formula you've used, every intermediate answer your calculator gives you - but it's much more tedious to have to retake your GCSE because you were one mark off of the grade you needed.

5. Use the formula sheet

On the front page of your exam is a handy-dandy list of formulas for prisms, cones, spheres, triangles, quadratics and sometimes trapeziums. Check what's on yours and make a point of looking there if you're stuck on a question with a weird shape.

6. Use your answer button

Down in the bottom right, by the equals sign, is one of the best buttons on your calculator: the Ans button. It means 'the last thing I worked out' - meaning, if you've done a complicated sum that's ended up with a long decimal answer, rather than have to type it back in again, you can just press Ans and the calculator will use the full answer. It's much easier to press Ans than to type in an infinitely long decimal answer, and the calculator almost always has better accuracy than you do. No offence meant!

7. Watch for negatives

Repeat after me: if $x = -2$, $x^2 = 4$. But, if you type $-2^2$ into the calculator, it'll give you $-4$. What gives?

Simple: you've broken the laws of BIDMAS1 $x^2$ means "multiply $x$ by itself" - while $-2^2$ means "the negative of the square of two." This catches people out all the time.

Another negative trap is that some calculators, when you press "-" at the start of a line, make it "Ans - ". It's better to use the negative key (usually one of the small buttons on the left, a couple of rows above the 7) when you're talking about a negative number.

8. Get good at proportions

I just looked at the November 2009 calculator paper (Linear 1380). Twenty-nine of the hundred marks - practically a third of the paper - could be gained using proportional reasoning (the Table of Joy or the Sausage Rule). Quick checklist, just for this paper:

  • Q8 'Best value' shopping (3)
  • Q10 Percentage increase (3)
  • Q13 Ratios (3)
  • Q21 Reverse percentages (3)
  • Q22 Similar shapes (4)
  • Q23 Finding an angle2 (3)
  • Q24 Stratified survey (2)
  • Q25 Direct proportion (4)
  • Q27 Histograms (4)

Phew - and that's without a currency conversion, a pie chart, a recipe, a map to scale, any probability, a density question, or a speed-distance-time thing.

9. Check your answers - it's easiest if they're neat

Everyone makes mistakes - in exams and in revising. I, believe it or not, mess up about 10% of the sums I do. Luckily, I have the good habit of checking to see if my answers make sense before I write them down. I still write down wrong answers sometimes - but then I go back through my working and check each step to make sure it's true.

I also have a terrible habit of not laying things out neatly, which makes it easier to mess up. When your handwriting is sloppy, it's easy to lose a minus sign, or turn an S into a 5.

Colin

Colin is a Weymouth maths tutor, author of several Maths For Dummies books and A-level maths guides. He started Flying Colours Maths in 2008. He lives with an espresso pot and nothing to prove.

  1. Which is bollocks. []
  2. I appreciate not everyone would do this proportionally []

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