Sam has a bag of 10 coloured balls, four are red and six are blue. Sam then picks two balls from the bag. What is the probability that Sam gets: I) Two red balls II) One red and one blue III) One red THEN one blue in that order.

First the student should draw a frequency tree with the appropriate information. This is not required for marks but shows clear understanding. The probabilities are as follows below:Red then Red: 2/15Red then Blue: 4/15Blue then Red: 4/15Blue then Blue: 1/3 or 5/15The answers are therefore:I) 2/15II) 4/15 + 4/15 = 8/15III) 4/15