To repair a roof that is 4 meters high, Mr. Russo leans a 5-meter ladder against the side of the building. To reach the roof, how far away from the building should he place the base of the ladder?

Answer 1

x^2 + 4^2 = 5^2
x = 3

You should make a point to memorize the right-angled triangle with sides
3-4-5 as the smallest right-angled triangle with integer sides