Whats the hypotenuse of a right triangle if both its legs are 9 cm round to the nearest tenth of a cm

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