In trapezium $ABCD$,$AB \parallel CD$. If $\angle A = 70^{\circ}$ and $\angle B = 85^{\circ}$,then $\angle D = \ldots$ (in $^{\circ}$)

$PQRS$ is a rectangle. If $PQ = 20 \, cm$ and $\operatorname{ar}(PQRS) = 300 \, cm^2$,then $SP = \dots \, cm$.

$P$ is the mid-point of the side $CD$ of a parallelogram $ABCD$. $A$ line through $C$ parallel to $PA$ intersects $AB$ at $Q$ and $DA$ produced at $R$. Prove that $DA = AR$ and $CQ = QR$.

The angles of a quadrilateral are in the ratio $3:4:6:5$. Find the measure of the greatest angle. (in $^\circ$)

Prove that the sum of angles of any convex quadrilateral is $360^{\circ} .$

Can all the angles of a quadrilateral be right angles? Give reason for your answer.