In an isosceles triangle ABC, the lateral side of AB is 2.5 times its base AC

In an isosceles triangle ABC, the lateral side of AB is 2.5 times its base AC, and the perimeter is 42 cm. Find the lateral side AB (in cm).

An isosceles triangle is a triangle whose two sides are equal. These sides are called sides, and the third side is the base.

Let the base of an isosceles triangle AC equal x cm, then the lateral side AB or BC is 2.5x cm.By the problem statement, it is known that the perimeter of a triangle is equal to (the perimeter of a triangle is equal to the sum of the lengths of its three sides) P = (2.5x + 2.5x + x) cm or 42 cm. Let’s make an equation and solve it.

2.5x + 2.5x + x = 42;

6x = 42;

x = 42: 6;

x = 7 (cm) – AC base;

2.5x = 7 * 2.5 = 17.5 (cm) – lateral side AB or BC.

Answer. 17.5 cm.