A rectangle has a perimeter of 70 centimeters and a length of 21 centimeters. What is its width?

1 Answer

The width is 14 cm.

Explanation:

Let's call l the length and w the width.

The perimeter p is the sum of two times the width plus two times the length:
p=2l+2w

We know that p=70 and l=21, so we can substitute these quantities in the equation and get
70=2 cdot 21 +2w
70=42+2w
28=2w
14=w