Question

A rectangle's length and width are in a ratio of 3:1. The perimeter is 72 inches. What are the length and width?

Answer 1

Explanation:

If the sides exist in a ratio to one another, then when you multiply some number x by both the length and the width, they still remain as a ratio. The length will be 3x and the width will be 1x. The perimeter formula is

P = 2L + 2W and since our perimeter is 72 and we have both the length and the width, we can fill in the formula and solve for x:

72 = 2(3x) + 2(1x) and

72 = 6x + 2x and

72 = 8x so

9 = x.

If x = 9, then 1x = 9 and 3x = 27. Let's check the perimeter against those side lengths.

P = 2(3x) + 2(1x) and

P = 2(27) + 2(9) and

P = 54 + 18 so

P = 72

and you're done! (The bold numbers above are the width and length, respectively.)