A spherical balloon with an initial radius r of 5 inches begins to leak at time t = 0, and its radius t seconds later is r = (60-t)/12in. At what rate (in cubic inches/second) is air leaking from the balloon when t = 30?

Please help!

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- February 8th 2010, 09:41 AMpoitierRate air leaks from balloon.
A spherical balloon with an initial radius r of 5 inches begins to leak at time t = 0, and its radius t seconds later is r = (60-t)/12in. At what rate (in cubic inches/second) is air leaking from the balloon when t = 30?

Please help! - February 8th 2010, 10:51 AMskeeter
- February 8th 2010, 12:15 PMpoitier
Thank you! That helps a lot. But how do I find dr/dt? How do I know that it equals (-1/12)?

- February 8th 2010, 01:16 PMArchie Meade
Hi poitier,

differentiate your given formula for r with respect to t.

This isn't one of those balloons that start off spherical and up end sausage-shaped as the air escapes i hope!