The frame of a picture is 30 cm by 36 cm outside. If the area of the picture (inner rectangle) is 480 square cm, what is the width of the uniform border?

Answer 1

let the border be x cm wide

picture is (30-2x) by (36-2x)
(30-2x)(36-2x) = 480
1080 - 132x + 4x^2 - 480 = 0
4x^2 - 132x + 600 = 0
x^2 - 33x + 150 = 0
solve using the quadratic equation,