Question

The hypotenuse of a 45-45-90 triangle measures 10√5 in.

Answer 1

This is the equation all worked out with the trick to 45 45 90 triangles to the side.

the answer is B

Answer 2

Let x be the length of one leg ⇒
By the Pythagorean theorem:

x² + x² = (10√5)²
2x² = 500
x² = 500/2
x² = 250
x = √250 = 5√10