Find all School-related info fast with the new School-Specific MBA Forum

It is currently 30 Jun 2015, 02:19

Close

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A number is selected at random from the set of integers{

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 14 Dec 2004
Posts: 119
Followers: 1

Kudos [?]: 12 [0], given: 0

A number is selected at random from the set of integers{ [#permalink] New post 25 Sep 2005, 08:20
A number is selected at random from the set of integers{ 1,2,3,... 1000}. What is the probability that it is divisible by 4 but neither by 5 nor by 7?
VP
VP
avatar
Joined: 22 Aug 2005
Posts: 1120
Location: CA
Followers: 1

Kudos [?]: 46 [0], given: 0

 [#permalink] New post 25 Sep 2005, 08:47
33/200

there are 1000/4 = 250 numbers divisible by 4
there are 1000/(4*5) = 50 numbers divisible by both 4 & 5
there are 1000 / (4*7) = 35 numbers divisible by both 4 & 7
there are 100/lcm(35, 50) or 1000/350 = 7 numbers divisible by both 5 & 7
there are 1000/ lcm (4, 20, 35) or 1000/700 numbers divisible by all 4, 5 & 7

numbers divisible by 4 but not by 5 or 7 = 250 - (50 + 35) + 7 + 1 = 172

p = 172/1000 or 0.172

Last edited by duttsit on 25 Sep 2005, 10:41, edited 2 times in total.
Director
Director
avatar
Joined: 23 Jun 2005
Posts: 847
GMAT 1: 740 Q48 V42
Followers: 5

Kudos [?]: 36 [0], given: 1

 [#permalink] New post 25 Sep 2005, 08:56
Is it 7/40?
I get the probability of getting a number divisible by 4 as 1/4 and the probability of getting a number divisible by 4 AND either 5 or 7 as 3/40. So, subtracting the latter from the former, I got the answer.

Last edited by anandsebastin on 25 Sep 2005, 09:01, edited 1 time in total.
Manager
Manager
avatar
Joined: 14 Dec 2004
Posts: 119
Followers: 1

Kudos [?]: 12 [0], given: 0

 [#permalink] New post 25 Sep 2005, 08:58
This one is from a textbook which only gives the OA, no explanation.

The OA is 0.172.
Manager
Manager
avatar
Joined: 14 Dec 2004
Posts: 119
Followers: 1

Kudos [?]: 12 [0], given: 0

 [#permalink] New post 25 Sep 2005, 11:44
Posted below:
Attachments

ans.jpg
ans.jpg [ 127.96 KiB | Viewed 484 times ]

  [#permalink] 25 Sep 2005, 11:44
    Similar topics Author Replies Last post
Similar
Topics:
Seven different numbers are selected from the integers 1 to marcodonzelli 10 12 Jan 2008, 04:37
Set X = Set Y = If a number is chosen at random from Set X bmwhype2 2 02 Nov 2007, 11:39
Set S = If a number is selected from set S at random and bmwhype2 14 24 Oct 2007, 11:56
Two numbers are successively selected at random and with young_gun 3 23 Oct 2007, 05:59
Two numbers are successively selected at random and with cloaked_vessel 4 28 Oct 2005, 17:35
Display posts from previous: Sort by

A number is selected at random from the set of integers{

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

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®.