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February 28, 2015

February 28, 2015

Posted by **Branden** on Friday, August 26, 2011 at 1:27pm.

And

The radius of a circle is decreasing at a rate of 2 ft/minute. Find the rate at which the area is decreasing with respect to time when the radius is 4 feet?

- Calculus -
**Reiny**, Friday, August 26, 2011 at 2:11pmV = (4/3)πr^3

dV/dt = 4πr^2 dr/dt

given dV/dt = 10 ft^3/min

so at r = 4

10 = 4π(16) dr/dt

dr/dt = 10/(64π) or appr. .05 ft/min

If A = 4πr^2, do the second question the same way.

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