PROBABILITY-

Expert replies

adssaini: Junior | Next Rank: 30 Posts; Posts: 20; Joined: Tue Aug 04, 2009 6:18 pm; Thanked: 2 times

by adssaini » Tue Aug 04, 2009 6:21 pm

Q. if the probability of rain on any given day is 50%, what it the probability that it rains exactly on 3 days in 5-day period.

Answer is 5/16

but I could not able to understand the a way solution is explained. Can anyone help me out ?

Thanks

Like this post

Source: Beat The GMAT — Problem Solving | Tue Aug 04, 2009 6:21 pm

apoorva.srivastva: Master | Next Rank: 500 Posts; Posts: 146; Joined: Wed Aug 27, 2008 5:41 am; Thanked: 3 times

Re: PROBABILITY-

by apoorva.srivastva » Wed Aug 05, 2009 1:10 am

[quote="adssaini"]Q. if the probability of rain on any given day is 50%, what it the probability that it rains exactly on 3 days in 5-day period.

Answer is 5/16

but I could not able to understand the a way solution is explained. Can anyone help me out ?

Thanks[/quote]

C(5,3) (.2)^3 * (.2)^2 = 5/16

Like this post

adssaini: Junior | Next Rank: 30 Posts; Posts: 20; Joined: Tue Aug 04, 2009 6:18 pm; Thanked: 2 times

Re: PROBABILITY-

by adssaini » Wed Aug 05, 2009 5:42 am

apoorva.srivastva wrote:
C(5,3) (.2)^3 * (.2)^2 = 5/16

Hi Apoorva,

Could you please explain this...I am not able to get this...

(.2)^3 * (.2)^2 = .00032

how you got 5/16 ?

thanks.

Like this post

apoorva.srivastva: Master | Next Rank: 500 Posts; Posts: 146; Joined: Wed Aug 27, 2008 5:41 am; Thanked: 3 times

by apoorva.srivastva » Wed Aug 05, 2009 7:46 am

C(5,3) * (.2)^3 * (.2)^2 = .00032

C(5,3) = 10

so 10* * (.2)^3 * (.2)^2 = .00032

Please post questions in either PS forum or Ds forum....more ppl will be able to help u!!

Like this post

srisanj4: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Sat Dec 27, 2008 3:38 pm

by srisanj4 » Wed Aug 05, 2009 7:49 pm

Probability that it rains all 5 days = 1/2 * 1/2 * 1/2* 1/2 * 1/2

we need to find probability of raining exactly 3 days - in no particular order... which is 5 C 3 = 5*4*3/3*2*1 = 10

Probability of raining 3 days exact in 5 day period = 10 * 1/2^5 = 5/16

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review