The two sides of the triangle have the same length, equal to 60 dm. The perimeter of the triangle is 1600 cm.

The two sides of the triangle have the same length, equal to 60 dm. The perimeter of the triangle is 1600 cm. Find the length of the third side.

Let x denote the length of the third side of this triangle.
According to the condition of the problem, the perimeter of this triangle is 1600 cm, which in decimeters is:
1600/10 = 160 dm.
It is also known that the two sides of a triangle have the same length, equal to 60 dm, therefore, we can draw up the following equation:
x + 60 + 60 = 160.
We solve the resulting equation and find the length of the unknown side of this triangle:
x + 120 = 160;
x = 160 – 120;
x = 40 dm.
Answer: the length of the third side of this triangle is 40 dm.