Engineering Board Exam Reviewer · Related Rates (Time Rates) · medium
Air is pumped into a spherical balloon so that its volume increases at 200 cm3/s. How fast is the radius increasing when the diameter is 20 cm?
- 1/2π cm/s 0.159 cm/s
- 1/π cm/s
- 0.5 cm/s
- 0.318 cm/s
Answer
A. 1/2π cm/s 0.159 cm/s
Solution
At diameter 20, r=10. dV/dt=4π r2dr/dt. 200=4π(100)dr/dt dr/dt=1/2π 0.159 cm/s.
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