Given :-
PR∥PQT⇒PQTR is a trapezium.
we know that a diagonal divides trapezium into two eqal areas .
⇒ar(ΔPQT)=ar(ΔPRT)=or(PQR)=ar(PTR)=12[ar(PQTR)] .....(i)
HS,
ar(PQRS)⇒ar(ΔPQR)+ar(ΔPSR)
⇒ar(ΔPTR)+ar(ΔPSR) .....[from(i)]
⇒ar(ΔPST)
=RHS
∴ar(PQRS)=ar(ΔPST)