Question 63277
In a rigth angled triangle, 

(hypotenuse)^2 = sum of the squares of the sides

(hypotenuse)^2 = 3^2 + 4^2

hypotenuse^2 = 9 + 16

hypotenuse ^2 = 25

Taking the square root , we get

hypotenuse = sqrt(25)

hypotenuse = 5