# The length of the lateral side of an isosceles triangle is 18 cm, and its perimeter is more than 65 cm

**The length of the lateral side of an isosceles triangle is 18 cm, and its perimeter is more than 65 cm. How long can the base of the triangle have?**

To answer this question, let us first recall some of the properties of isosceles triangles. In particular, the fact that an isosceles triangle is called a triangle in which two sides are equal, as well as the fact that equal sides of an isosceles triangle are called lateral, and not an equal side – the base. Also, remember that the perimeter is the sum of the lengths of all the sides of the shape. That is, to find how long the base of a given triangle can have, it is necessary to multiply the length of the side by two and subtract the result from the given perimeter. Let’s calculate:

18 * 2 = 36

65 – 36 = 29

Answer: the length of the base of the given triangle must be more than 29 centimeters.