Question

Rewrite the perimeter formula, P = 2/ + 2w, to solve for the length, I, and then

use this formula to find the length of a rectangle whose width is 7 inches and
perimeter is 42 inches.

Answer 1

P = 2l + 2w

Subtract both sides by 2w

P - 2w = 2l

Divide both sides by 2

(P - 2w) / 2 = l

In our problem,

w = 7 in

P = 42 in

Let's plug our values into the formula above.

(42 in - 2(7 in) / 2 = l

(42 in - 14 in) / 2 = l

28 / 2 = l

14 in = length