Question
A hollow cylinder has an internal radius of 7 cm and an
external radius of 10 cm. If its height is 20 cm, find the total surface area of the cylinder.Solution
The total surface area of a hollow cylinder is given by: TSA = 2πh(R + r) + 2π(R² - r²) Where h = 20 cm, R = 10 cm (external radius), r = 7 cm (internal radius). TSA = 2π(20)(10 + 7) + 2π(10² - 7²) = 2π(20)(17) + 2π(100 - 49) = 680π + 2π(51) = 680π + 102π = 782π cm² ≈ 782 × 3.14 ≈ 2455.48 cm² Correct Option: d
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