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What is the probability of picking at least one white ball

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Re: What is the probability of picking at least one white ba

by parallel_chase » Sun Dec 28, 2008 2:52 pm
nh8404052006 wrote:If two balls are to be choosen from 3 red balls and 2 white balls, what is the probability of picking at least one white ball?

at least 1 white = probability of picking 1 white + probability of picking 2 white


Probability of picking 1 white

2C1 * 3C1 / 5C2 = 6/10

Probability of picking 2 white

2C2 / 5C2 = 1/10


total probability = 6/10 + 1/10 = 7/10

Hope this helps.
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by cramya » Sun Dec 28, 2008 2:53 pm
2C1->PICKING 1 WHITE BALL FROM 2
3C1->PICKING 1 RED BALL FROM 3

2C2->PICKING 2 WHITE BALLS FROM 2

5C1->NUMBER OF WAY 2 BALLS CAN BE PCIKED FROM 5

2C1*3C1 + 2C2 / 5C2

= 7/10


(OR)
P(atleast one) = 1 - p(none) where p(none) is pciking red ball first and red ball second

= 1- 3/5*2/4
= 7/10
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by kishore » Sun Dec 28, 2008 8:39 pm
If two balls are to be choosen from 3 red balls and 2 white balls, what is the probability of picking at least one white ball?


Answer: probability of picking at least one white ball is

1 - (probability of picking only red ball)

1 - ( 3C2/5C2) = 1- (3/10) = 7/10
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by vittalgmat » Sun Dec 28, 2008 11:36 pm
The quickest way to solve probability problems which have "atleast" is to do the 1 - P(something else happening all the time), if that is possible, and most of the times it is possible.

I find this approach very scalable.

just my opinion.

Thanks
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