Work out the base of a square with area, A = 225cm2.
really....
\(A = s^2 \\ 225 = s^2 \\ s = \pm \sqrt{225} \\ s = \pm 15 \\ \text{negative lengths don't make sense}\\ s = 15\)
Work out the area of a rectangle with base, b = 18mm and perimeter, P = 50mm.