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The volume of the metal of a cylindrical pipe is 748 cm3. The length of the pipe is 14cm and its external radius is 9 cm. Its thickness is (Take π = 22/7)
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- 1 cm
- 5.2 cm
- 2.3 cm
- 3.7 cm
- 1 cm
Correct Option: A
Let the thickness of the pipe be x cm
∴ If the external radius = 9 cm then, in radius = (9 – x) cm
According to the question, π × 9² × 14 – π × 14 × (9 – x)² = 748
↠ π × 14 (81 – (81 + x² – 18x)) = 748
π p × 14 (–x² + 18x) = 748
| ⇒ –x² + 18x = | = | |||
| π × 14 | 22 × 14 |
⇒ –x² + 18x = 17
⇒ x² – 18x + 17 = 0
⇒ x² – 17x – x + 17 = 0
⇒ x (x – 17) – 1 (x – 17) = 0
⇒ (x – 1) (x – 17) = 0
⇒ x = 1 or 17 but x = 17 is inadmissible
∴ x = 1 cm
