In a class of 60 students there are 33 girls. The average weight of these girls is 62 Kg and average weight of the full class is 66.5 kg. What is the average weight of the boys of the class?
Find the power of a convex lens if the image formed is at a distance of 20 cm from the lens when the object is placed on the other side of the lens at 25 cm from the optical centre?