Question

The length of a rectangle is 4 mm less than 3 times the width. If the perimeter is 56 mm, what is the length of the rectangle?

Answer 1

Explanation:

l = length

w = width

l = 3w - 4

the perimeter of a rectangle (the way all around the rectangle) is 2 times the length and 2 times the width.

56 = 2l + 2w

now we are using the first equation and substitute it into the second

56 = 2×(3w - 4) + 2w = 6w - 8 + 2w = 8w - 8

64 = 8w

w = 8 mm

=>

l = 3w - 4 = 3×8 - 4 = 24 - 4 = 20 mm