A spherical mothball evaporates uniformly at a rate proportional to its surface area. Hence deduce a differential equation that links its radius with time. Given that the radius halves in one month, how long will the mothball last?

Thanks :)

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- November 4th 2008, 03:58 PMeugeniusDifferential Equation Problem
A spherical mothball evaporates uniformly at a rate proportional to its surface area. Hence deduce a differential equation that links its radius with time. Given that the radius halves in one month, how long will the mothball last?

Thanks :) - November 4th 2008, 05:22 PMskeeter
- November 4th 2008, 05:26 PMeugenius
thanks, i'll see how i get on

- November 5th 2008, 12:50 AMeugenius
i still cant do the last bit, help please :S

- November 5th 2008, 02:18 AMmr fantastic