Enigma 1696: Leftovers
From New Scientist #2863, 5th May 2012 [link]
A set of snooker balls contains six coloured and 15 red balls. From such a set Harry took some coloured balls and a larger number of reds and put them in his bag. From the remainder Tom took some coloured balls and some reds (more of each than Harry took) and put them into his bag.
Each of them calculated that if he drew two balls at random out of his own bag simultaneously there was a 1 in X chance that they would both be coloured, X representing the same number for each person.
How many coloured balls and how many red balls from the set were not taken by either of them?
This is probably the same Harry and Tom from Enigma 1551.