# Math

A bag contain three black balls,four white balls and five red balls.Three balls are removed without replacement.What is the probability of obtaining
a)one of each colour
b)at least two red balls?

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1. So you want BWR
that particular order's prob = (3/12)(4/11)(5/10) = 1/22
but the BWR can be arranged in 3! or 6 ways.
so Prob(your event) = 6/22 = 3/11

b) could RRB or RRW

prob(RRB in that order) = (5/12)(4/11)(3/10) = 1/22
we it could have been RRB, RBR, BRR, so
prob(of RRB in any order) = 3/22
do the same for RRW, then add them up

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👨‍🏫
Reiny

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