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

What is the median of a triangle?

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

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

What are the properties of a parallelogram?

Think about the area of a parallelogram and a triangle.

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

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

Think about the area of a parallelogram.

Recall the properties of triangles having equal areas.