This is in continuation of A Cup Of Coffee.

You have a five cup mug, a three cup mug, a water supply, a sink with a drain, and a packet of instant coffee which when dissolved in one cup of water produces coffee of strength 100%.

The packet may be used at any time, but the entire contents of the packet must be dissolved into a single mug when it is used.

What integer values of c (from 1 to 25 inclusively) is possible if the task is to fix 4 cups of coffee at exactly c% strength? Prove that these are indeed the only possible values of c.

(In reply to possible solution by Dej Mar)

The restriction to 25% or less is not arbitrary, but is imposed by the situation, where you want 4 cups of coffee but have only 1 packet of instant coffee. Anything above 25% is impossible.

Posted by Charlie on 2012-03-07 10:39:52