Find the perimeter of an isosceles triangle, the two sides of which are 30 cm and 15 cm.

The perimeter of a triangle is the sum of all its sides. In an isosceles triangle, the two sides are equal. Two sides of the triangle are given a = 15 cm, b = 30 cm.

1. What is side c equal to? In a triangle, the sum of the lengths of any two sides is greater than the third.

a) if c = a, then

a + c> b;

2a> b, replace a, b with numerical values:

2 × 15> 30,

30> 30, this is not true, 30 = 30.

c) check, for c = b:

2 × b> a;

2 × 30> 15;

60> 15, right, so c = b = 30 cm.

2. Find the perimeter:

P = a + b + c, or

P = a + 2 × b;

P = 15 + 2 × 30;

P = 15 + 60;

P = 75 cm.