It is all too easy to make silly mistakes during your GCSE/IGCSE maths exam. Obviously the fewer you make the better your result will be so here are some common ones to watch out for:
This is particularly true when solving equations. It is very easy to “lose” a minus sign by mistake part way through a solution so always check through your work afterwards.
Some ratio questions deal with the whole ratio and some deal with just one part so make sure you are clear which type you are dealing with.
One of the most common mistakes quoted by examiners is that of taking ⅛ to be equal to 30%
Make sure that any answers you give are sensible. Probabilities have to lie between 0 and 1 and they must be positive – any answer that is bigger than 1 or negative must be wrong. The mean of a list of numbers cannot be larger or smaller than all of the numbers in the list. When finding the missing side of a right angled triangle using either Pythagoras’ Rule or trigonometry the shorter sides cannot be longer than the hypotenuse.
For trigonometry at GCSE level (Higher papers only) your calculator should be in the “degrees” setting. This is usually denoted by a small D in a box – if yours has an R or a G instead you need to reset it.
A question which asks you to solve a quadratic equation correct to 3 significant figures (Higher paper only) is unlikely to be easily factorised so use the formula.
Tracing paper is allowed in all GCSE Maths exams so use it to check questions on transformations, especially rotations and reflections as it is very easy to get these wrong if you do them by sight.