Bayes with sampling without replacement

Questions involving conditional probability after selecting multiple items without replacement from containers (boxes, bags), where probabilities change after first selection.

1 questions

CAIE S1 2005 November Q2
2 Boxes of sweets contain toffees and chocolates. Box \(A\) contains 6 toffees and 4 chocolates, box \(B\) contains 5 toffees and 3 chocolates, and box \(C\) contains 3 toffees and 7 chocolates. One of the boxes is chosen at random and two sweets are taken out, one after the other, and eaten.
  1. Find the probability that they are both toffees.
  2. Given that they are both toffees, find the probability that they both came from box \(A\).