Question

The length of a rectangle is double its width. If the rectangle has a perimeter of 138cm, find its length (in cm).

Answer 1

length = 46cm

Explanation:

The length of a rectangle is double its width. If the rectangle has a perimeter of 138cm, find its length (in cm).

p = 2l + 2w

when l = 2w, substitute in to equation:

138 = 2(2w) + 2w

138 = 4w + 2w

138 = 6w

divide both sides by 6:

138/6 = 6w/6

so width = 23cm

and we know that length = 2 width so:

length = 23cm × 2

length = 46cm