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#