This is a problem about area, so you'll need a different formula:

where b is the base and h is the height.

The base and height are the two legs in a right triangle. You don't know the lengths exactly, but you do know that b + h = 20, so h = 20 - b. Substitute that into the formula:

Now solve by using the quadratic formula.

If , then .

If , then .

Now use the Pythagorean theorem to find the hypotenuse. (It doesn't matter which b you use, because you'll get the same answer.) Then add the sides together to find the perimeter.

01