A bag contains 5 red, 3 brown,6 yellow, and 2 blue marbles. Once a marble is selected, it is not replaced. Find the probability of pulling a red marble, and then a blue marble?

1 Answer
Adam
Mar 12, 2018

#7/240#

Explanation:

First establish the probability of pulling out each colour from a full bag.
#P(r) = (n(r))/(n(s)) = 5/16#
#P(br) = (n(br))/(n(s)) = 3/16#
#P(y) = (n(y))/(n(s)) = 6/16#
#P(bl) = (n(bl))/(n(s)) = 2/16#
Where #s# is the sample space.
The probability of pulling out a red marble is #5/16#.
Now the sample space (#s#) is reduced by one, as a red marble has been removed. The new #s# value is #15#.
Therefore, the probability of pulling out a blue marble is now #2/15#.
To find the probability of fulfilling both of these conditions, we multiply the probabilities:
#5/16 * 2/15 = 7/240#

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