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

 It is currently 26 Apr 2015, 21:45

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 June
Open Detailed Calendar

At a certain hospital, 75% of the interns receive fewer than

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Manager
Joined: 03 Jul 2007
Posts: 53
Followers: 1

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

At a certain hospital, 75% of the interns receive fewer than [#permalink]  25 Dec 2007, 21:01
1
This post was
BOOKMARKED
At a certain hospital, 75% of the interns receive fewer than 6 hours of sleep and report feeling tired during their shifts. At the same time, 70% of the interns who receive 6 or more hours of sleep report no feelings of tiredness. If 80% of the interns receive fewer than 6 hours of sleep, what percent of the interns report no feelings of tiredness during their shifts?

A, 6
B, 14
C, 19
D, 20
E, 81

Please explain in detail with your answer. I don't know if I can answer this question in 2 to 4 minutes. Is there is a quicker way to get to the answer. I tried the double-matrix table option.

thanks
CEO
Joined: 21 Jan 2007
Posts: 2764
Location: New York City
Followers: 9

Kudos [?]: 348 [0], given: 4

[#permalink]  25 Dec 2007, 21:25
see below
Attachments

a.jpg [ 12.34 KiB | Viewed 884 times ]

Manager
Joined: 21 Dec 2007
Posts: 99
Followers: 1

Kudos [?]: 14 [0], given: 0

Re: overlapping sets [#permalink]  27 Jan 2008, 07:22
i cant view the image..can sum1 plz re-explain the qstn..
SVP
Joined: 28 Dec 2005
Posts: 1583
Followers: 2

Kudos [?]: 86 [0], given: 2

Re: overlapping sets [#permalink]  27 Jan 2008, 08:21
im not sure what im doing wrong here, but the answer i get isnt one of the choices :-S

I assumed 100 total interns. 80% overall gets less than 6 hrs sleep, so thats 80 people. Of the 80, 75% feel tired ... thats 60 people who are tired, and 20 who arent.

Then we have 20 people who get more than 6 hours of sleep, but 70% of them, i.e. 14 people arent tired ... that leaves 6 people who are tired.

The total # of people who arent tired are the 20 people + 14 people = 34 people, which should be 34% ....
Director
Joined: 12 Jul 2007
Posts: 865
Followers: 12

Kudos [?]: 217 [0], given: 0

Re: overlapping sets [#permalink]  27 Jan 2008, 08:57
pinal2 wrote:
At a certain hospital, 75% of the interns receive fewer than 6 hours of sleep and report feeling tired during their shifts. At the same time, 70% of the interns who receive 6 or more hours of sleep report no feelings of tiredness. If 80% of the interns receive fewer than 6 hours of sleep, what percent of the interns report no feelings of tiredness during their shifts?

A, 6
B, 14
C, 19
D, 20
E, 81

Please explain in detail with your answer. I don't know if I can answer this question in 2 to 4 minutes. Is there is a quicker way to get to the answer. I tried the double-matrix table option.

thanks

Let's make this super easy guys. We'll say we have 200 interns.

200 interns
150 (75%) get fewer than 6 hours of sleep and report feeling tired
160 (80%) get fewer than 6 hours of sleep
40 (200-160) get more than 6 hours of sleep
28 (70% of 40) get more than 6 hours of sleep and don't report feeling tired

(160-150)+28 = 38 interns don't report feeling tired. (160-150 comes from 160 getting fewer than 6 hours of sleep, but only 150 of that number saying they feel tired. meaning 10 don't feel tired)
38/200 = 19%

Answer C
Director
Joined: 12 Jul 2007
Posts: 865
Followers: 12

Kudos [?]: 217 [0], given: 0

Re: overlapping sets [#permalink]  27 Jan 2008, 09:00
Quote:
I assumed 100 total interns. 80% overall gets less than 6 hrs sleep, so thats 80 people. Of the 80, 75% feel tired ... thats 60 people who are tired, and 20 who arent.

The question is saying 75% of the TOTAL receive fewer than 6 hours of sleep and report feeling tired. Then it says 80% get fewer than 6 hours of sleep, so 80-75 = 5% don't feel tired and get less than 6 hours of sleep.

Then you did the other part correctly and got 14% so 14+5 = 19%
Manager
Joined: 02 Jan 2008
Posts: 159
Followers: 2

Kudos [?]: 69 [0], given: 0

Re: overlapping sets [#permalink]  27 Jan 2008, 10:15
C is right

75 (st<6, tired: yes)
80 (st<6)

So, not tired with sleep time < 6 = 80 - 75 = 5 people

For Sleep Time>=6
80 (st < 6) so 20 (st >=6). Out of these 20, 70% report no tiredness so 20*70/100=14 people

Adding them, 14+5 = 19 people out of 100
Director
Joined: 01 May 2007
Posts: 794
Followers: 1

Kudos [?]: 119 [0], given: 0

Re: overlapping sets [#permalink]  27 Jan 2008, 17:17
You use a table to solve this. You want to pay attention to what you are taking percentages of, either the total or another number. If percent questions like this, that do not give a total, just pick a number. I picked 100.
--------------------Less 6 hours----More 6 hours--------------Total
Report Tired---------75%(100)---------blank------------------blank

No Report------------5----------------70%(x)-----------------Solve for

Total---------------80%(100)----------x----------------------100

Solve for the total of no report row. 19% C
Director
Joined: 03 Sep 2006
Posts: 885
Followers: 6

Kudos [?]: 256 [0], given: 33

Re: overlapping sets [#permalink]  27 Jan 2008, 18:22
pinal2 wrote:
At a certain hospital, 75% of the interns receive fewer than 6 hours of sleep and report feeling tired during their shifts. At the same time, 70% of the interns who receive 6 or more hours of sleep report no feelings of tiredness. If 80% of the interns receive fewer than 6 hours of sleep, what percent of the interns report no feelings of tiredness during their shifts?

A, 6
B, 14
C, 19
D, 20
E, 81

Please explain in detail with your answer. I don't know if I can answer this question in 2 to 4 minutes. Is there is a quicker way to get to the answer. I tried the double-matrix table option.

thanks

total number of interns = 100

Sleeping < 6 hrs = 75 ( all tired )

Therefore sleeing > 6 hrs = (100-75) = 25

Not tired = 70% of 25

Condition If Sleeping < 6 hrs = 80 ( all tired )

Therefore sleeing > 6 hrs = (100-80) = 20

Not tired = 70% of 20 = "14"

Further you know......
Re: overlapping sets   [#permalink] 27 Jan 2008, 18:22
Similar topics Replies Last post
Similar
Topics:
At a certain hospital, 75% of the interns receive fewer than 5 06 Dec 2008, 06:02
1 At a certain hospital, 75% of the interns receive fewer than 6 22 Sep 2008, 01:09
At a certain hospital, 75% of the interns receive fewer than 3 24 Mar 2008, 15:37
At a certain hospital, 75% of the interns receive fewer than 1 22 Mar 2008, 17:18
At a certain hospital, 75% of the interns receive fewer than 2 25 Aug 2007, 21:01
Display posts from previous: Sort by

At a certain hospital, 75% of the interns receive fewer than

 Question banks Downloads My Bookmarks Reviews Important topics

 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®.