Area of Trapezoids

Distance, Area, Volume Unit Study
Day 9: Area of Trapezoids

We broke trapezoids into rectangles and triangles to find the area.

Using a ruler to measure paper manipulatives makes learning about area so much easier. Discovery mathematics is a key to my son's success. Cutting out two triangles and giving them to him so he can discover they create a square works much better than telling him the area of a triangle is the area of a rectangle divided by two.

Continuing with the discovery method, the area of a trapezoid was calculated. First a trapezoid was measured to whole units and drawn on a sheet of paper inside a rectangle. The kids calculated the area by finding the area of the triangles in the corners and subtracting that area from the area of the rectangle. Then they recalculated the are by breaking the trapezoid into rectangles and triangles and adding the individual areas together.

Next, the kids discovered the biggest triangle that could be created from one rectangle.

Several rectangles were sketched and the length of the sides given.

The areas of the triangles were calculated and compared. In each example above, one triangle measured 16 square inches, and the sum of the remaining space totaled 16 square inches.