What is the perimeter of the triangle shown on the coordinate plane, to the nearest tenth of a unit?

24.8 units

27.8 units

28.5 units

30.9 units

To calculate the perimeter, consider each side separately.

Left side: This side is easiest - it's a straight vertical line that's 8 units long.

Top side: If you look carefully, this side is really the hypotenuse of a triangle that is 5 units tall and 9 units long. Using the Pythagorean Theorem, you can calculate the length of the hypotenuse to be 5^2 + 9^2 = c^2 - - > c = 10.3

Bottom side: Just like the top side, this side is the hypotenuse of a triangle that is 3 units tall and 9 units long. Pythagoras again: 3^2 + 9^2 = c^2 - - > c = 9.5

Add these sides up for the final perimeter: 8 + 10.3 + 9.5 = 27.8