Question

Which of the following sets of numbers could be the side lengths of a right triangle? 3, 4, and 7
9, 40, and 42
8, 15, and 16
20, 21, and 29

Answer 1

For a right triangle, the two shorter sides (the legs a and b) squared must add up to equal the longest side (the hypotenuse or c) squared. This is the pythagorean theorem:

a squared + b squared = c squared

If you try all the sets in the pythagorean theorem equation, 20, 21 and 29 are the only ones that work out, so that would be the answer.