The two sides of the triangle are 5/8 cm with a perimeter of 21/16 cm, find the length of the third side.

Let’s denote by x the length of the third side of this triangle.

According to the condition of the problem, the two sides of this triangle are 5/8 cm, and the perimeter of this triangle is 21/16 cm.

The perimeter of any triangle is equal to the sum of the lengths of all three sides of this triangle, therefore, we can draw up the following equation:

5/8 + 5/8 + x = 21/16.

We solve the resulting equation and find the length of the third side of this triangle:

10/8 + x = 21/16;

x = 21/16 – 10/8;

x = 21/16 – 20/16;

x = 1/16 cm.

Answer: the length of the third side of this triangle is 1/16 cm.