A 5 inch by 8 inch rectangle is enlarged to a similar rectangle whose smallest side measures 9 inches. What is the length in inches of the diagonal of the enlarged rectangle?

Answer 1

D1/D2 = 5/9

D1 = √(5^2 + 8^2) = √89

so √89/D2 = 5/9
5D2 = 9√89
D2 = 9√89/5

notice that the diagonal increased by a factor of 9/5 or the same as the increase in the sides.