Say the hypotenuse has length $h$ inches. By the Pythagorean Theorem, $h^2=20^2+21^2=400+441=841$, so $h=\sqrt{841}=29$. The length is thus $\boxed{29}$ inches.
A right triangle has legs measuring 20 inches and 21 inches. What is the length of the hypotenuse, in inches?
{'answer': '29', 'subject': 'Prealgebra', 'level': 3, 'unique_id': 'train/prealgebra/553.json'}