Surface Areas and Volumes EXERCISE 13.3 Q1: Diameter of the base of a cone is 10.5 cm and its Slant Height is 10 cm. Find its curved Surface area. Answer: Given r = 10.5/2 = 5.25 cm, l = 10 cm. Curved surface area (CSA) of the cone = πrl = (22/7) × 5.25 × 10  = 165 cm² (Answer) Q2: Find the total surface area of a cone, if its slant height is 21 m and diameter of its base is 24 m.