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probability Q-1

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probability Q-1

by speed » Mon Aug 27, 2007 8:54 pm
help me to solve these probability questions

1.In a bag of balloons, the ratio of red balloons to other colours is 1:5, if 3 balloons are selected from the bag at random, what is the probability that (a) at least one balloon is red, (b) exactly one balloon is red.?

speed
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by ratindasgupta » Mon Aug 27, 2007 10:53 pm
Assume that 1 balloon is red and there are 5 balloons of other colours.

Atleast 1 red = 1 - (no red)

No red = 5/6 x 4/5 x 3/4 = 1/2

Atleast 1 red = 1- 1/2 = 1/2


Exactly 1 red = (1C1 x 5C2)/6C3 = 1/2

Whats the OA?
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