A box contains four green marbles, eight blue marbles and six, orange marbles. What is the probability that the first two picked will be orange followed by blue? (no replacement)

The probability of something occurring is calculated by dividing the number of ways that thing can happen by the total number of ways anything can happen. So for the first pick you succeed by pulling any one of the 6 orange marbles out of the 18 marbles in the bag. Hence the probability of that happening is 6/18. Now for the second pick there are 8 blue marbles out of the 17 that are still in the bag. So - what's the probability of getting a blue? Finally the probability of getting both an orange on the first draw and a blue on the second is equal to these two probabilities multiplied together.

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