A rectangle on a coordinate grid has corners at (1, 2), (9, 2), (9, 5) and (1, 5). Enter the number of square units in its area.

Explication

The width is the gap between 1 and 9 across, and the height is the gap between 2 and 5 up, so the rectangle measures 8 by 3. Entering 22 gives the distance right round the outside, which counts each side once rather than measuring the squares held inside.