Pythagorean theorem: a² + b² = c²
a² and b² are the legs, and c² is the hypotenuse.
Plug in 9 to a² and b² since you know that both the right triangle's legs are 9 cm.
9² + 9² = c²
81 + 81 = c²
162 = c²
Square root both sides.
c = 12.7 cm
fans bought 5/8 so there is 3/8 still left
45000 * 3/8 = 16,875 seats are left
