Just use the properties of shapes on the same base.

Recall the properties of triangles having equal areas.

Remember median of a triangle divides the triangle into two triangles of equal area.

What are the properties of a rectangle?

Use the properties of median of a triangle.

What happens when two parallelograms are on the same base and between the same parallels?

What do we mean by common base for parallelogram and triangle ?

What is the median of a triangle?

What happens when two parallelograms are on the same base and between the same parallels?

Recall the properties of parallelograms and median of a triangle.