One of the things I often notice when marking examination papers is that students generally get the numerical parts of questions right. I suppose this shouldn’t be too surprising, as maths and physics together make a popular A-level combination and I would expect most physics students to be competent mathematicians. And yet mistakes are sometimes made. Very often, it seems to me, these are not the consequence of an underlying mathematical problem but are instead caused by arithmetical errors. In this article I am going to take a break from my usual discussion of more challenging topics and instead try to give you a few hints that may enable you to avoid some of the more common mistakes.
Part of the problem is that we rely very much on calculators, and yet calculators cannot think for themselves — they only do what they are told, and exactly what they are told. If the instructions are wrong then so will be the answer. This is neatly summed up in the GIGO principle — Garbage In, Garbage Out. You may think that you never give the calculator the wrong instructions, but in my experience it’s very common. In a single class I’ve sometimes had six or seven different answers to the same question — all caused by pressing the wrong buttons, or forgetting the rules of BODMAS. You need to check!
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