OCR S1 2007 January — Question 7

Exam BoardOCR
ModuleS1 (Statistics 1)
Year2007
SessionJanuary
TopicTree Diagrams
TypeMulti-stage with stopping condition

7 A bag contains three 1 p coins and seven 2 p coins. Coins are removed at random one at a time, without replacement, until the total value of the coins removed is at least 3p. Then no more coins are removed.
  1. Copy and complete the probability tree diagram. First coin
    \includegraphics[max width=\textwidth, alt={}, center]{43f7e091-9ae7-4373-a209-e2ebdba5260f-4_350_317_1279_568} Find the probability that
  2. exactly two coins are removed,
  3. the total value of the coins removed is 4p.