In an isosceles triangle, the perimeter is 36 cm, find the base if the side is exactly 15 cm.

1. The statement of the problem speaks of an isosceles triangle.

For such a figure, the length of the two sides is equal.

These sides are called lateral and each, in accordance with the condition of the problem, is 15 cm.

Let’s calculate the sum of the two sides of the triangle.

15 + 15 = 30 cm.

2. The perimeter of a triangle is equal to the sum of the lengths of its three sides.

The perimeter is known to be 36 centimeters.

Determine the length of the third side – the base of the isosceles triangle.

36 – 30 = 6 cm.

Answer: The length of the base of an isosceles triangle is 6 cm.