Answer:
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