When you find the area of a triangle using the "Rectangle" method, this means you find the area of a rectangle with similar dimensions and divide to find the area of your original triangle. This can be accomplished in a few minutes with a calculator and the appropriate mathematical formula. Area is measured in "square" units, depending on the original unit used. For example, if the sides of your triangle are measured in inches, the area would be in square inches.
Things You'll Need
 Tape measure
 Calculator

Measure the length of the base side of your triangle. Place one end of the tape measure on one side of the base and measure the distance across to the other side. Write down this number on a piece of paper.

Measure the height of your triangle. This is found by measuring the side of the triangle that is perpendicular to the base. Place one end of the tape measure at the bottom of the triangle and measure the distance across to the top. Write this number down on a piece of paper.

Multiply your base measurement by your height measurement together. The number you get is the area for a rectangle that has identical measurements to your triangle. For example, a base of 8 inches multiplied by a height of 6 inches would result in an area of 48 square inches.

Divide your result from Step 3 by 2. This finds the area of just the triangle and not the imaginary rectangle you created during your measurements. For example, 48 square inches divided by 2 is equal to an area of 24 square inches for your triangle.