Multiple choice

A cylindrical water tank is open at the top. Its curved surface area is 396 m2. The height of the tank is 21 m. Ignoring the thickness of the material used for building the tank, find the total cost of painting the outer surfaces of the tank at the rate of Rs. 14 per m2 if the outer bottom part of the tank is also included.

  1. Rs. 4,050

  2. Rs. 5,940

  3. Rs. 6,950

  4. Rs. 5,500

  5. Rs. 6,500
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Curved Surface Area = 2*pi*r*h = 396. With h=21, 2*pi*r*21 = 396, so r = 396 / (42*pi) = 3 m. The total area to paint is CSA + Area of base = 396 + pi*r^2 = 396 + 9*pi. Using pi approx 22/7, 396 + 9*(22/7) = 396 + 28.28 = 424.28. Cost = 424.28 * 14 = 5940.

Keep practicing — related questions