Probability of picking 2 red balls and 3 blue?

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r_walid: Senior | Next Rank: 100 Posts; Posts: 43; Joined: Wed Jan 21, 2009 2:24 pm; Thanked: 1 times

by r_walid » Wed Nov 11, 2009 3:40 pm

There are 5 red balls and 10 blue balls.
if one is to pick 5 balls, What is the probability of picking 2 red and 3 blue?

please explain your reasoning.

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Source: Beat The GMAT — Problem Solving | Wed Nov 11, 2009 3:40 pm

getso: Master | Next Rank: 500 Posts; Posts: 141; Joined: Sat Feb 28, 2009 8:19 am; Thanked: 1 times

by getso » Thu Nov 12, 2009 12:12 am

Is it 400/1001

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raghavakumar85: Senior | Next Rank: 100 Posts; Posts: 58; Joined: Tue Sep 30, 2008 10:19 am; Thanked: 7 times; GMAT Score:630

by raghavakumar85 » Thu Nov 12, 2009 1:15 am

Probability = no. of desired outcomes / total no. of outcomes.

no.of desired outcomes = (5c2) x (10c3)
total no. of outcomes = (10+5)c5 = 15c5

Probability = (5c2 x 10c3)/ 15c5 = 400/1001

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m3tm4n: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Sun Nov 13, 2011 5:00 am

by m3tm4n » Sat Nov 19, 2011 2:40 am

Hi,

I understand the use of combination formula (easy to solve btw).

But is it possible to solve this problem without using the Combination formula? Just to understand this topic.

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