PQRS PQRS\,PQRS is a trapezium where PQ PQ\,PQ is parallel to SR SR\,SR and the angle ∠PSR=90∘\angle PSR = 90^\circ∠PSR=90∘.
PQ=10PQ = 10PQ=10 cm, SR=18SR = 18SR=18 cm, and QR=15QR = 15QR=15 cm.
Calculate the length of the diagonal PRPRPR.
Give your answer correct to 3 significant figures.