Answer
B. 5√ 7
Explanation
When solving the lengths of a right triangle we use either the trigonometric ratio or the pythagoras theorem.
c² = a² + b²
Where a and b are the legs of the triangle and c is the hypotenuse.
20² = 15² + b²
b² = 20² - 15²
= 400 - 225
= 175
b = √175
= √(25 × 7)
= 5√7 inches
