Question
Outer diameter of 20 cm long pipe is 25 cm. If the
thickness of the metal in the pipe is 1 cm. Find the total surface area of the pipe?Solution
Outer part surface area = 2πRh Inner part surface area = 2πrh Area of shaded portion = 2πR² - (πr)² = π(R² - r²) Total surface area = 2πRh + 2πrh + 2π(R² - r²) = 2π(R+r) [h + R - r] = 2π(R+r) [h + thickness] Required surface area = 2π(R+r) [h + thickness] = 2 × 22/7 × (12.5 + 11.5) × 21 = 132 × 24 = 3168
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