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. Accuracy 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. Probability 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. Mean 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.