Another one for you guys. Probability

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Kaunteya: Senior | Next Rank: 100 Posts; Posts: 36; Joined: Mon Jan 28, 2008 4:12 pm; Location: Montreal, Canada; Thanked: 2 times

Another one for you guys. Probability

by Kaunteya » Thu Feb 28, 2008 3:36 pm

On Saturday morning, Bill will begin a camping vacation and he will return home at the end of the first day on which it rains. If on the first three days of the vacation the probability of rain on each day is 0.2, what is the probability that Bill will return home at the end of the day on the following Monday?
A. 0.008
B. 0.128
C. 0.488
D. 0.512
E. 0.640

Again another one for you guys to tackle.

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Source: Beat The GMAT — Problem Solving | Thu Feb 28, 2008 3:36 pm

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pm; Location: Toronto; Thanked: 1710 times; Followed by:614 members; GMAT Score:800

Re: Another one for you guys. Probability

by Stuart@KaplanGMAT » Thu Feb 28, 2008 10:17 pm

Kaunteya wrote:On Saturday morning, Bill will begin a camping vacation and he will return home at the end of the first day on which it rains. If on the first three days of the vacation the probability of rain on each day is 0.2, what is the probability that Bill will return home at the end of the day on the following Monday?
A. 0.008
B. 0.128
C. 0.488
D. 0.512
E. 0.640

Again another one for you guys to tackle.

The question is asking us "what's the probability that Monday is the first day on which it rains?"

So, we want:

no rain on Saturday, no rain on Sunday, rain on Monday.

so: (.8)(.8)(.2) = (.64)(.2) = .128

Last edited by Stuart@KaplanGMAT on Fri Feb 29, 2008 1:24 pm, edited 1 time in total.

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

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codesnooker: Legendary Member; Posts: 543; Joined: Fri Jan 18, 2008 1:01 am; Thanked: 43 times; GMAT Score:580

by codesnooker » Thu Feb 28, 2008 10:26 pm

Thanks Stuart

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Kaunteya: Senior | Next Rank: 100 Posts; Posts: 36; Joined: Mon Jan 28, 2008 4:12 pm; Location: Montreal, Canada; Thanked: 2 times

by Kaunteya » Fri Feb 29, 2008 8:08 am

Thanks Stuart, that is what I got, but there was no answer to the question. I think I am finally sort of getting the hang of probability, permutations and combination. Could you do me a favour? Could you please post up a few permutation, combination and probability questions that you find that the REAL GMAT may test. That way I can decide if my knowledge on this material is strong enough. Thanks mate.

Kaunteya