A roller is shaped like a cylinder. Let h be the height of the roller and r be the radius. h = Length of roller = 120 cm Radius of the circular end of roller = r = (84/2) cm = 42 cm Now, CSA of roller = 2πrh = 2×(22/7)×42×120 = 31680 cm2 Area of field = 500×CSA of roller = (500×31680) cm2 = 15840000 cm2 = 1584 m2. Therefore, area of playground is 1584 m2. Answer! A cylindrical pillar is 50 cm in diameter and 3.5 m in height. Find the cost of painting the curved surface of the pillar at the rate of Rs. 12.50 per m2. (Assume π = 22/7) Solution: Let h be the height of a cylindrical pillar and r be the radius. Given: Height cylindrical pillar = h = 3.5 m Radius of the circular end of pillar = r = diameter/2 = 50/2 = 25cm = 0.25m CSA of pillar = 2πrh = 2×(22/7)×0.25×3.5 = 5.5 m2 Cost of painting 1 m2 area = Rs. 12.50 Cost of painting 5.5 m2 area = Rs (5.5×12.50) = Rs.68.75 Therefore, the cost of painting the curved surface of the pillar at the rate of Rs. 12.50 per m2 is Rs 68.75. Curved surface area of a right circular cylinder is 4.4 m2. If the radius of the base of the base of the cylinder is 0.7 m, find its height. (Assume π = 22/7) Solution: Let h be the height of the circular cylinder and r be the radius. Radius of the base of cylinder, r = 0.7m CSA of cylinder = 2πrh CSA of cylinder = 4.4m2 Equating both the equations, we have 2×(22/7)×0.7×h = 4.4 Or h = 1 Therefore, the height of the cylinder is 1 m.