In Fig., PQRS and ABRS are parallelograms and X is any point on side BR. Show that (i) ar (PQRS) = ar (ABRS) (ii) ar (AXS) = $\frac{1}{2}$ ar (PQRS)                   

If a triangle and a parallelogram are on the same base and between the same parallel lines, the area of the triangle will be half of that of a parallelogram or if two parallelograms are on the same and between two parallel lines then their area will be equal. 

i) It can be observed from the figure that parallelogram PQRS and ABRS lie on the same base SR and also, they lie between the same parallel lines SR and PB.

According to Theorem 9.1, Parallelograms on the same base and between the same parallel lines are equal in area.

∴ Area (PQRS) = Area (ABRS)   .....(1)