A rectangle has an area of 36 cm2. The length of the rectangle is 4 times the width. Solve for the width W (in cm) of the rectangle.

Answer 1

Length is 4Width

l=4w

4w.w=36

4w²=36

w²=9

w=3

Answer 2

Let x be the width and y the length of the rectangle. By assumptions we have that xy=36 and y=4x which implies that x(4x)=36 or equivalently, 4x^2=36. Thus, x^2=9 and since x represents length (it must be positive) we get x=3 and y=12.