I am taking S1 on Friday.
and I got stuck on question 7 in Jan 07.
Question as follow:
A bag contains three 1p coins and seven 2p 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)Complete the probability tree diagram.
first coin
1p: 3/10 -
2p: 7/10 -
Find the probability that
2) exactly two coins are removed.
3) the total value of the coins removed is 4p.
thanks