Roses are shipped in packages of 9 roses, each containing 3 red roses and 6 whit
ID: 3271545 • Letter: R
Question
Roses are shipped in packages of 9 roses, each containing 3 red roses and 6 white roses. A florist asks
his color-blind assistant (who cannot tell the difference between red and white roses) to arrange two
such packages into 3 bouquets, each containing 6 roses. Since the assistant cannot distinguish red
from white, assume that all possible groupings of the 18 roses into groups of 6 are equally likely.
(a) What is the probability that the 3 bouquets produced by the assistant each contain exactly two
red roses?
(b) What is the probability that any 2 of the 3 bouquets produced by the assistant contain the
same number of red roses?
Explanation / Answer
(a) The various options for the 6 red roses to go into the 3 bouquets are:
0-0-6 : 3 ways
0-1-5 : 6 ways
0-2-4 : 6 ways
0-3-3 : 3 ways
1-1-4 : 3 ways
1-2-3 : 6 ways
2-2-2 : 1 way
Probability of having two roses in each bouquet = 1/25 = 0.04
(b) In the combinations above, 0-0-6, 0-3-3,1-1-4, 2-2-2 have same number of roles
Probability = (3+3+3+1)/25 = 10/25 = 2/5
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