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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

At a certain hospital, 75% of the interns receive fewer than [#permalink]

Show Tags

25 Dec 2007, 22:01

1

This post was BOOKMARKED

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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.

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% ....

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%

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%

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

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......

gmatclubot

Re: overlapping sets
[#permalink]
27 Jan 2008, 19:22