The external and internal diameters of a hollow cylindrical pipe are 14 cm and 12 cm‚ respectively. What is the volume of iron used to make the pipe if the height of the pipe is 21 cm? (Use π = 22/7)
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Correct answer: D
Explanation
The correct answer is option 4 i.e 858 cu. cm.
External diameter = 14 cm → radius = 7 cm
Internal diameter = 12 cm → radius = 6 cm
Height = 21 cm
Volume of iron = π × (R² - r²) × height = (22/7) × (7² - 6²) × 21
⇒ (22/7) × (49 - 36) × 21
⇒ (22/7) × 13 × 21
⇒ (22 × 13 × 21) ÷ 7 = 6006 ÷ 7 = 858 cm³