Using the equation a² +b² = c² The lengths of a and b are always smaller than c. We know that the hypotenuse is the longest side, making it c, meaning 3 and 5 are the opposite and adjacent sides. Therefore, we substitute our numbers into the equation, 3² + 5² = c². = 9 + 25 = c² c² = 34 c = √34, which is equal to 5.83 (to the nearest hundredth)