You are creating a metal border of uniform width for a wall mirror that is 20 inches by 24 inches. You have 416 square inches of metal to use. Write and solve an equation to find the border's width.

Answer 1

final dimensions of the framed mirror:
(20+2w) x (24+2w)

final area: (20+2w)(24+2w)
mirror area: 20*24
border area: (20+2w)(24+2w)-480
= 480 + 88w + 4w^2 - 480 = 416
w^2 + 22w - 104 = 0
(w+26)(w-4) = 0

w = 4