Question

The surface of an office desk has a perimeter of 20 feet and an area of 21 square feet. what are the dimensions of the desk?

Answer 1

3 feet by 7 feet

Explanation:

perimeter = 20 feet

area = 21 feet²

If the desk is a rectangle:

perimeter = 2l + 2w = 2 (l+w) = 20

2 (l+w) = 20 , divide both sides by 2

l+w = 10

area = l · w = 21

What numbers we know that have sum as 10 and their product as 21?

l + w = 10

l · w = 21

factors of 21 are 1,3,7

3+7 = 10

3 ·7 = 21

The dimensions of the desk could be 3 feet by 7 feet.