“Who would draw a picture to divide 2/3 by 3/4?” asked Marina Ratner, a professor emerita of mathematics at the University of California at Berkeley, in a recent Wall Street Journal opinion piece.

There are two rules to remember when adding or subtracting fractions. The fractions need to have a common denominator. This means the denominator has to be the same. You only need to add or subtract ...

Click to see a step-by-step slideshow. Image caption, STEP 1 - When adding fractions it can be useful to visualise it. Draw a square with 4 columns and shade in one of the columns. This represents ¹/₄ ...