Q1. A bag contains some coloured balls. There are 2 black, 4 blue, 2 green, 3 red, 2 yellow, 1 orange, 1 brown and 1 purple ball. From this information work out the following probabilities:


(a) A ball selected at random will be green.


First of all we need to add up the number of balls in the bag. A quick mental addition should tell you that there are 16 balls in total. From this 16 balls we can see the 2 of them are green, so the probability of choosing a green ball is given by:



(b) A ball selected at random will be blue or green.


In the same way as for the previous part of the question, we need to examine the number of possible ways in which a blue or a green ball can be pulled out. The 4 blue and 2 green gives us a total of 6 possibilities that the ball will be one or the other. The total number of ways that we can pull out any ball is of course 16 so the probability of the ball being blue or green:



(c) A ball selected at random will NOT be purple.


This final part of the question can be approached in 2 ways. First of all there is 1 purple ball in the bag so we can see that the probability of pulling it any other, must be 15/16. The alternative way to look at this is to take away the probability of pulling out purple from the probability of pulling out anything (which of course is a certainty, you have to pull something out):



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