The radius of a spherical balloon is increasing at the rate of 0.5 cm/s. The rate of increase of its surface area when the radius is 10 cm is:
The radius of a spherical balloon is increasing at the rate of 0.5 cm/s. The rate of increase of its surface area when the radius is 10 cm is:
- A. 40π cm²/s
- B. 20π cm²/s
- C. 10π cm²/s
- D. 80π cm²/s
Answer: A) 40π cm²/s
Explanation: Surface area S = 4πr². dS/dt = 8πr (dr/dt) = 8π × 10 × 0.5 = 40π cm²/s.
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