AP Calculus ABeasystimulus-mcq1 pt

A spherical balloon is being inflated at a rate of 10π10\pi cubic centimeters per second. At what rate is the radius of the balloon increasing when the radius is 55 cm?

A.0.10.1 cm/sec
B.0.20.2 cm/sec
C.0.40.4 cm/sec
D.0.50.5 cm/sec

Explanation

Core Concept

Correct. Differentiating volume gives dVdt=4πr2drdt\frac{dV}{dt} = 4\pi r^2 \frac{dr}{dt}. Substituting 10π=4π(5)2drdt10\pi = 4\pi(5)^2 \frac{dr}{dt} yields 10π=100πdrdt10\pi = 100\pi \frac{dr}{dt}, so drdt=0.1\frac{dr}{dt} = 0.1.

Correct Answer

A0.10.1 cm/sec

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