Answer:
29 inches
Explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
h² = 20² + 21² ( h is the hypotenuse )
= 400 + 441 = 841 ( take the square root of both sides )
h =
= 29