If 'P 3 Q' means 'P is daughter of Q', 'P 5 Q' means 'P is father of Q', 'P 7 Q' means 'P is mother of Q' and 'P 9 Q' means 'P is sister of Q', then how is J related to K in J 3 L 9 N 3 O 5 K?
Find the power of a convex lens if the image formed is at a distance of 16 cm from the lens when the object is placed on the other side of the lens at 20 cm from the optical centre?