Hello zcus05

Welcome to Math Help Forum!I am assuming the the phrase 'half of a snowball' refers to half the volume, not that the radius has been halved (which would reduce the volume to one-eighth of its original value).

The surface area and volume formulae are:

The rate of decrease of volume is proportional to the surface area is translated as:

If the initial volume is , then:

, where is the initial radius.

So when :

So, assuming we measure time in hours, when :

When :

So the time taken for the remainder to melt is:

hours.If, after all, the phrase 'half the snowball' meant that theradiushas been halved, then, of course the additional time taken would be one hour, since the radius is decreasing at a constant rate.

Grandad