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If the radius of a sphere is increased by 2 cm, then its surface area increases by 352 cm². The radius of the sphere initially was : (use π = 22/7)
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- 4 cm
- 5 cm
- 3 cm
- 6 cm
- 4 cm
Correct Option: D
Initial radius of sphere = r cm (let).
According to the question, 4π(r + 2)² – 4πr² = 352
⇒ 4π ((r + 2)² – r²) = 352
| ⇒ r² + 4r + 4 – r² = | |
| 4π |
| = | ||
| 4 × | ||
| 7 | ||
| ⇒ 4r + 4 = | = 28 | |
| 4 × 22 |
⇒ 4r = 28 – 4 = 24
| ⇒ r = | = 6 cm | |
| 4 |
