GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 17 Feb 2019, 08:21

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

## Events & Promotions

###### Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT Algebra Webinar

February 17, 2019

February 17, 2019

07:00 AM PST

09:00 AM PST

Attend this Free Algebra Webinar and learn how to master Inequalities and Absolute Value problems on GMAT.
• ### Valentine's day SALE is on! 25% off.

February 18, 2019

February 18, 2019

10:00 PM PST

11:00 PM PST

We don’t care what your relationship status this year - we love you just the way you are. AND we want you to crush the GMAT!

# If the probability of rain on any given day in Chicago

 post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
Manager
Joined: 01 Nov 2007
Posts: 126
If the probability of rain on any given day in Chicago  [#permalink]

### Show Tags

23 Jan 2008, 13:11
1
00:00

Difficulty:

(N/A)

Question Stats:

85% (00:26) correct 15% (00:37) wrong based on 79 sessions

### HideShow timer Statistics

If the probability of rain on any given day in Chicago during the summer is 50%, independent of what happens on any other day, what is the probability of having exactly 3 rainy days from July 4 through July 8, inclusive?
(A) 1/32
(B) 2/25
(C) 5/16
(D) 8/25
(E) 3/4

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Director
Joined: 01 Jan 2008
Posts: 588
Re: PS - Probability  [#permalink]

### Show Tags

23 Jan 2008, 13:25
1
C is the answer.
C(5,3)/2^5 = (5!/(3!*2!))/2^5 = 10/32=5/16
Director
Joined: 14 Oct 2007
Posts: 721
Location: Oxford
Schools: Oxford'10
Re: PS - Probability  [#permalink]

### Show Tags

23 Jan 2008, 13:39
maratikus wrote:
C is the answer.
C(5,3)/2^5 = (5!/(3!*2!))/2^5 = 10/32=5/16

don't get it. can you explain further please
Director
Joined: 01 Jan 2008
Posts: 588
Re: PS - Probability  [#permalink]

### Show Tags

23 Jan 2008, 13:48
buffdaddy wrote:
maratikus wrote:
C is the answer.
C(5,3)/2^5 = (5!/(3!*2!))/2^5 = 10/32=5/16

don't get it. can you explain further please

read about binomial distribution:

http://en.wikipedia.org/wiki/Binomial_distribution
Intern
Joined: 03 Jan 2008
Posts: 7
Re: PS - Probability  [#permalink]

### Show Tags

23 Jan 2008, 14:02
1
Here, there are 5 days from July 4 to July 8.
The prob of rains is given as 50%, i.e: 1/2.

There are 10 possible ways to pick 3 days (when it rains) from 5 days,
i.e 5C3 = 5!/3!2! = 10.

So the probability for any one of the ten combinations would be:
1/2*1/2*1/2*1/2*1/2 = 1/32

So the prb for all 10 combinations are:
1/32 * 10 = 5/16.

Ans: C
Intern
Joined: 03 Jan 2008
Posts: 7
Re: PS - Probability  [#permalink]

### Show Tags

23 Jan 2008, 14:06
It is the 'or' rule used here, i.e: It can rain on 4th, 5th and 7th or 4th, 6th and 8th etc.
So you would be adding 1/32 ten times.
Intern
Joined: 03 Jan 2008
Posts: 7
Re: PS - Probability  [#permalink]

### Show Tags

23 Jan 2008, 14:11
Same logic as in this one:

A man can hit a target once in 4 shots. If he fires 4 shots in succession, what is the probability that he will hit his target?

A. 1
B. 1/256
C. 81/256
D. 175/256
E. 144/256
Director
Joined: 03 Sep 2006
Posts: 778
Re: PS - BINOMIAL DISTRIBUTION  [#permalink]

### Show Tags

23 Jan 2008, 22:46
The binomial distribution applies when:

1: The number of observations n is fixed.
2: Each observation is independent.
3: Each observation represents one of two outcomes ("success" or "failure").
4: The probability of "success" p is the same for each outcome.

If these conditions are met, then X has a binomial distribution with parameters n and p, abbreviated B(n,p).

$$nCx *(p)^x*(1-p)^(n-x)$$

n= 5
x=3
p=1/2

Or if you want to go by logic,

No. of ways in which it can rain on 3 days out of 5 is

5C3 = 10ways

10 * ( 1/2)^3 * (1-1/2)^2 = 10/32

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Non-Human User
Joined: 09 Sep 2013
Posts: 9837
Re: If the probability of rain on any given day in Chicago  [#permalink]

### Show Tags

06 Feb 2019, 00:40
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: If the probability of rain on any given day in Chicago   [#permalink] 06 Feb 2019, 00:40
Display posts from previous: Sort by

# If the probability of rain on any given day in Chicago

 post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.