Area of Triangles and Parallelograms

Over the last couple of days, we have been learning about how to find the area of triangles and parallelograms. First, we reviewed about how to find the area of a rectangle using the formula:

Area = Base x Height

Once students understood this, then we cut a piece of paper from one corner to an opposite corner to find out that we get two identical triangles. From this, we learned that the area of a triangle is exactly half of a rectangle that has the same base and height. We derived the formula:

Area or triangle = Base x Height / 2

Finally, we positioned the two triangles to make a parallelogram! This told us that the area of a parallelogram and the area of a rectangle are the same, so we can use the same formula:

Area = Base x Height

One part that challenged many students today was using the formula to help find the missing side of a parallelogram or triangle when given the area. Here is a video I made to help students better understand how to solve these types of problems:


Here is a link to a Blendspace unit that covers many of the concepts for this unit:




Here is a Blendspace unit that covers finding the area of Triangles: