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

Perpendicular distance between two parallel lines is the shortest distance between those line.

Think about the area of a parallelogram.

Think about the area of a parallelogram and a triangle.

Recall the properties of triangles having equal areas.

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

Just use the property of relationship between parallel sides of a trapezium.

Recall the property of a triangle and parallelogram on the same base and between the same parallels.

Recall that the quadrilateral so formed after joining the mid points of a parallelogram is also a parallelogram.Also recall its relation to that of the external parallelograms.

What are the properties of a parallelogram?