Question

The length of a rectangle is

9
inches more than
4
times the width. If the area of the rectangle is
100
square inches, find the length and the width.

Answer 1

l = 3w + 9

A = 210 = lw

Substitute:

210 = (3w + 9) w

210 = 3w^2 + 9w

3w^2 + 9w - 210 = 0

Quadratic formula or factor. 3(w - 7)(w + 10) = 0

w = 7

(w = -10, ignore this answer as a width cannot be negative)

l = 30

Explanation: