Question #N170
A square has side length 10. What is the length of the diagonal of the square?
A. 10
B. 10$\sqrt{2}$
C. 20
D. 100
Correct Answer is: B
A diagonal of a square divides the square into two 45-45-90 right triangles. The ratio of the length of a leg to the length of the hypotenuse in a 45-45-90 triangle is 1:$\sqrt{2}$. Therefore, the length of the diagonal of the square, which is the hypotenuse of the 45-45-90 triangle, is $10\sqrt{2}$.