Two bags contain different numbers of red and blue marbles. A marble is removed from one of the bags. The marble is blue. What is the probability that it was removed from bag A?
You and I play a game involving successive throws of a fair coin.
Suppose I pick HH and you pick TH. The coin is thrown repeatedly
until we see either two heads in a row (I win) or a tail followed
by a head (you win). What is the probability that you win?
Jewellery Boxes
Age 14 to 16 Short Challenge Level
Two boxes, P and Q, each contain 3 jewels.
When a jewel worth £5000 is transferred from P to Q, the average value of the jewels in each box increases by £1000.