Well done those who said 3, as, yes its, 3. Jason Hedges answered it most comprehensively so a litre of Cillet Bang goes to him in the first class post....
So one pull gets u either a white or black, the next? could be an odd one of the one you've already pulled, BUT the third is guarenteed to match one or the other you previously took out the bag.
Anyway, its a good one.
Dan