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Qube

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## Homework Statement

http://i4.minus.com/jboxzSadIJVVoi.jpg

## Homework Equations

Product rule; implicit differentiation.

Volume of cylinder, V = pi(r^2)(h)

## The Attempt at a Solution

dV/dt = 0 = pi[2r(dr/dt)(h) + (dh/dt)(r^2)]

Solve the equation after plugging in r = 5; h = 8, and dh/dt = -2/5. Solve for dr/dt.

0 = 80pi(dr/dt) - 10pi

1 = 8(dr/dt)

dr/dt = 1/8

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