Question

Two sides of a triangle are equal in length, and the third side is 5 inches. If the perimeter is 17 inches, how long are the two equal sides?

Answer 1

You know the length of one side is 5in and are trying to find the length of the other two side (which, conveniently, are equal!).

Perimeter of a triangle can be found by adding up all three sides of the triangle. That means if you know the length of one side, subtracting that length from the perimeter gives you the length of the other two sides added up. So:

`P = s1 + s2 + s3`

`17 = 5 + s2 + s3`

`12 = s2 + s3`

Since you know the two mystery sides are the same length, just divide 12 by 2. 12/2 = 6in. That means each one of the two equal sides is 6in long.