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?
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?
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A spherical mothball evaporates uniformly at a rate proportional to its surface area.
since
equating ...
so, the radius decreases at a constant rate ... can you take it from here?