Will is a maths teacher at Merchant Taylors' Boys' School, Crosby, Liverpool.
Almost everyone who studied maths at school will at some point have bumped into BIDMAS or its twin, BODMAS.
BIDMAS stands for Brackets, Indices (powers), Division and Multiplication, Addition and Subtraction. BODMAS is identical, except “indices” are called “Order”. Both acronyms tell us the same thing: the order in which to tackle the operators in an equation.
For example, in the sum 1 + 22 - (3 + 2) x 4, we must first evaluate the contents of the brackets. Indices (powers) would be next, then division and multiplication, then finally addition and subtraction.
This order of precedence is crucial in all arithmetic. To do things in a different order (to start solving the above sum by doing 1 + 2, for example) would often lead to a different and incorrect answer.