What is the length of the longer base of the larger trapezoid?

Question

The ratio of the perimeters of two similar isosceles trapezoids is 4:5. The longer base of the smaller trapezoid has a length of 9cm .What is the length of the longer base of the larger trapezoid?

Answer 1

Since the trapezoids are similar, lets use a proportion.

 

The ratio of perimeters = the ratio of the longer bases.  If the ratio of perimeters is 4:5, then the ratio is smaller trapezoid to larger trapezoid.

 

(4 / 5) = (9 / x)

 

Cross multiply.

 

4x = 45

  x = 11.25

 

The length of the longer base of the larger trapezoid is 11.25 cm.