In a right triangle, if the two legs are 3 and 4, what is the length of the hypotenuse?

Use the PYTHAGOREAN THEOREM: a² + b² = c², where c is the hypotenuse. Here: 3² + 4² = c² → 9 + 16 = 25 = c². So c = √25 = 5. ASVAB Mathematics Knowledge tests the Pythagorean theorem. The 3-4-5 triangle is the most common 'Pythagorean triple' and appears frequently — worth memorizing (along with 5-12-13 and 6-8-10). Strategy: square the two legs, add them, then take the square root to find the hypotenuse. The hypotenuse is always the longest side, opposite the right angle.