GCSE Maths Exam Tips

The following list is by no means complete but these are some points to bear in mind when answering GCSE maths exam questions.

How to avoid common mistakes

Always read the question

I know this may sound obvious but it always surprises me how often students don’t read a question. They see a diagram and ignore any comments about it or any earlier notes and rush straight in. It can often be a good idea to highlight or tick off each point as it is read, so that you don’t miss anything.


Always check after you finish a question that you are giving the answer to required degree of accuracy that was asked for. It may be 3 significant figures, 1 decimal place etc. Why lose an accuracy mark unnecessarily?

Rounding Errors

When a question involves several stages of working where answers end in long decimals, DO NOT round up. If you use the rounded value again in another part of the question it will cause the next answer to be slightly out. Instead write answers at any stage as un-rounded values so if the calculator gives an answer such as 23.456782314 simply write 23.4567. Use this or your calculator value in further calculations to avoid rounding errors.

Simultaneous equations

Most questions that are set will give nice answers, usually integer values. If you get horrible decimals then suspect your answer and check again. It is quite likely that you have made a mistake somewhere.

Inverse percentage questions

These are questions where you have to calculate the original value before an increase or decrease has taken place. These can be tricky but you should be able to tell if you have made a mistake as the answers are almost always a clean answer. Get a long decimal that needs rounding and the chances are you have made a mistake.


When calculating a probability, check that your answer always lies between 0 and 1. 0 means the event will never happen and 1 that it is guaranteed to happen. I am still surprised how many times I see students give answers more than 1 and are quite happy to accept it.


When calculating the mean from a set of data make sure your answer lies between the lowest and highest values of the set of data. If it is outside this range it must be wrong.

Cumulative frequency graphs

Always plot points based on the upper bounds of any class intervals, NOT midpoints.

Solving Quadratic Equations

When a question says solve the following quadratic giving answers to 3 significant figures or several decimal places then do not waste time trying to factorise it. It will not factorise. Instead, use the quadratic formula.

Pythagoras’ Theorem

When finding a shorter side of a right angled triangle check that the answer is smaller than the hypotenuse. If not then the chances are you added rather than subtracted the squares of the two other sides.


When calculating a side of a right angled triangle. Check that it looks sensible. If it is a smaller side it should not be larger than the hypotenuse.

Bold Print Comments in a Question

If a question contains bold print then take care as it is trying to draw your attention to a specific point where it may be very easy to trip up. For example it is common to see the following question on cumulative probability. Find the number of people less than 150 cm tall. You would simply read off the value. However, Find the number of people who are more than 150 cm tall requires a little more care. Take your answer for how many are less than 150 cm away from the total number of people.

Tracing Paper

Get some tracing paper. Most exam boards allow you to take this in to the GCSE maths exam. It is often overlooked and can be useful for rotating shapes about a point.

Setting out your work

Try to write reasonably small as there is often very little space to show your working. Always show working, as this is likely to give you method marks. No working and you could be throwing away marks. Try not to write down what may appear to be random calculations. The following statements mean nothing 50×2 = 100 100-3 = 97 Instead, try to give an introduction to a calculation, such as Area of rectangle = 50×2 = 100 cm squares Set work out in columns if possible, drawing a line between columns to separate your working.


A selection of video tutorials for your GCSE maths exam can be found here.