There are 9 counters in a bag. 7 of the counters are green. 2 of the counters are blue. Two counters are chosen at random, what is the probability one counter of each colour is chosen.

There are two methods to pick one counter of each. Either pick the (1)green counter first and then blue, or a (2)blue counter first and then green. We must calculate the probability of both of these scenarios and then add the two together for the answer.(1) Probability of picking Green and then Blue: 7/9 x 2/8 = 14/72(In the second probability the denominator is 8 as we have already picked a counter making the total number of counters in the bag 8)(2) Probability of picking Blue and then Green:2/9 x 7/8 = 14/72(Once again the same rule applies as above. The second denominator is one lower as a counter has been removed from the bag)To find out the probability of picking one of each colour, we must add the probabilities of the two scenarios together:14/72 + 14/72 = 28/72Answer = 28/72