Get to know your calculator
Hopefully you’ve been working with this very same calculator for five years or so and you know it like the back of your hand. You should still double check a few things;
- Is it set to work with degrees? Look for a little D at the top of the screen.
- Do you know where to find the fraction button? The π button? The button to use for standard form?
- Did you know you can use your calculator to write a number as a product of its prime factors? Look for the button with the word FACT above it. This can save you some time when working with factors and multiples.
Most calculators are pretty clever and will know to apply the order of operations to any calculation. But do be careful with negative numbers. For example, some calculators may evaluate -22 as -4. We know that’s wrong, since squaring a negative number gives a positive result. Instead, pop some brackets around the negative number to be safe: (-2)2.
Show all your working
I know, you’ve been told this all before. And it certainly is tempting to pop everything into your calculator and write down the answer. However, if you get it wrong you will lose all available marks on that question. Instead, make sure you write down each step you’ve taken. It’s time consuming but the working out can be worth over 80% of the marks on a big question so it’s worth the extra few seconds it will take.
Don’t round too early
When completing a long calculation, it can be tempting to round any values to 1 decimal place to make them easier to work with. This can have a huge effect on the final answer to the question, and can even lose you the final accuracy mark. Instead, use the ANS button on your calculator to recall a previous answer, or use a number with as many decimal places as you can.
If you calculator gives 2.918112412, don’t be tempted to use 2.9. Instead, use 2.9181124 in your next calculation.
Estimate before and after
Before you get started on a question, check whether you can estimate the solution so you can check the suitability of any answers you get.
“A taxi firm charges a call out fee of £7.50, then charges £2.10 per mile. How much would the taxi firm charge for a journey of 25 miles?”
Begin by rounding each value to one significant figure. £7.50 rounds to £8, £2.10 rounds to £2 and 25 miles rounds to 30 miles.
Next, use these numbers to estimate a solution: £8 + (£2 × 30) = £76.
Now you have a rough idea of the size your actual answer should be and can use this to quickly decide whether your answer is likely to be correct.
And while we are there, check your work at least once!
Once you have finished, spend some time looking back over your work and checking for silly mistakes. It’s worth remembering too that exam boards will mark the working that relates to any answer on the answer line. This means that, if you’ve got two methods and you aren’t sure which one is correct, leave them both but do not write anything on the answer line. The solution which gains you the most marks will be the one that is marked!
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