What is the internal surface area value of the cylindrical tank with diameter 65 ft and height 24 ft?

• A. 11,531.65 ft^2
• B. 10,000 ft^2
• C. 12,000 ft^2
• D. 9,500 ft^2

Answer: (A)

Internal surface area of a closed cylinder comes from the curved side plus both circular ends. So calculate the radius from the diameter: r = 65/2 = 32.5 ft, height h = 24 ft.

Curved surface area = 2πrh = 2π × 32.5 × 24 = 1560π ft^2.

End caps area = 2πr^2 = 2π × (32.5)^2 = 2112.5π ft^2.

Total internal surface area = 1560π + 2112.5π = 3672.5π ft^2 ≈ 1,152.5 × π ≈ 11,537 ft^2.

The closest option is about 11,531.65 ft^2.