SOLUTION: The length of a rectangle is 2 times longer than its width. If the diagonal of the rectangle measures 21 inches, what is its length?

Algebra ->  Rectangles -> SOLUTION: The length of a rectangle is 2 times longer than its width. If the diagonal of the rectangle measures 21 inches, what is its length?       Log On


   

Question 943979: The length of a rectangle is 2 times longer than its width. If the diagonal of the rectangle measures 21 inches, what is its length?
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
the diagonal of the rectangle forms a right triangle with length and width as legs
so L^2+W^2=diagonal^2
W=width; L=length=2W; Diagonal=d=21 inches
Substitute for L:
%282W%29%5E2%2BW%5E2=d%5E2
4W%5E2%2BW%5E2=%2821%29%5E2
5W%5E2=441
W%5E2=441%2F5
W=sqrt%28441%2F5%29
L=2W=2%2Asqrt%28441%2F5%29=42%2Fsqrt%285%29 ANSWER