Find the leg of the triangle if the hypotenuse is 25cm and the other leg is 20cm.

Since the leg and hypotenuse are indicated in the problem, it means that the triangle is rectangular.

We can use the Pythagorean theorem: the sum of the squares of the legs is equal to the square of the hypotenuse. Let us denote the unknown leg by the letter X, then

25 ^ 2 = 20 ^ 2 + X ^ 2

625 = 400 + X ^ 2

X ^ 2 = 625 – 400

X ^ 2 = 225

X = 15

leg is 15 cm