Why is it that a lot of students forget vital working out when answering GCSE Maths questions? Well the answer is that students think that by putting a single answer down that they will get all the marks possible for that question! How wrong is that!
The simple truth is that examiners are looking for students to demonstrate that they are able to apply a method to solve a mathematical problem, hence examiners award marks for doing so even if you arive at the wrong answer!!
Remember that Mathematics is fundamentally about accuracy, not speed. Therefore under timed examination conditions it is far better to spend time showing all working out and checking your answer and working out afterwards, than rushing the question and only putting an answer down that could potentially be wrong! So you may end up with no marks with just a single answer! So as you can see it really makes sense to show your working out!