 It is currently 26 Mar 2019, 04:44 ### 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

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. # Re: In a survey,it was found that 10% of the students who a  Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Intern Joined: 01 Mar 2017
Posts: 3
Followers: 0

Kudos [?]: 0 , given: 16

Re: In a survey,it was found that 10% of the students who a [#permalink] 00:00

Question Stats: 0% (00:00) correct 100% (01:55) wrong based on 1 sessions
harigrestudent97 wrote:
In a survey,it was found that 10% of the students who are susceptible to tuberculosis are less than 20 years of age and 40% of the students who are not susceptible to tuberculosis are more than or equal to 20 years of age.If 9% of the total students are more than or equal to 20 years of age and are susceptible to tuberculosis,then what percentage of the students,that are 20 years old or more,are not susceptible to tuberculosis?

A) 20%
B) 36%
C) 45%
D) 54%
E) 80%
[Reveal] Spoiler: OA GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783  , given: 397

Re: In a survey,it was found that 10% of the students who a [#permalink]
1
KUDOS
Expert's post
Please share the source of the question. The question seems to be strangely worded.
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Intern Joined: 10 Apr 2017
Posts: 1
Followers: 0

Kudos [?]: 0 , given: 0

Re: In a survey,it was found that 10% of the students who a [#permalink]

Try to assume a certain number of students i.e 100. The question states 10 % are susceptible and are less than 20 years of age. Hence the student count becomes 90. The question then states that 40 % are not susceptible and are more then 20 years of age. Hence we get 36 students from this statement.Finally the question states 9 % of total students are susceptible and more than 20 years of age, which yields 9. Hence the percentage of students not susceptible and are more than 20 years of age is 36/45 x 100 = 80 %. Answer is E
Director Joined: 03 Sep 2017
Posts: 521
Followers: 1

Kudos [?]: 344 , given: 66

Re: In a survey,it was found that 10% of the students who a [#permalink]
This question seems to be very popular on other GRE forums, unless there is no source specified anywhere.

However, here is my try:

We know 9% of the total are >20 and susceptible (so 9 out of our hypothetical 100 people). We know these 9 are 90% of the susceptible (b/c we're told that 10% of the susceptible are <20). That means there must be 10 total susceptible.

How many of the remaining 90 are not susceptible? 40% according to the question, so 36.

Then, we can take this 36 and divide by the total number of people >20:

36/[9 + 36] = 0.8, or 80%.

Target Test Prep Representative Status: Head GRE Instructor
Affiliations: Target Test Prep
Joined: 09 May 2016
Posts: 161
Location: United States
Followers: 4

Kudos [?]: 125 , given: 0

Re: In a survey,it was found that 10% of the students who a [#permalink]
Expert's post
harigrestudent97 wrote:
harigrestudent97 wrote:
In a survey,it was found that 10% of the students who are susceptible to tuberculosis are less than 20 years of age and 40% of the students who are not susceptible to tuberculosis are more than or equal to 20 years of age.If 9% of the total students are more than or equal to 20 years of age and are susceptible to tuberculosis,then what percentage of the students,that are 20 years old or more,are not susceptible to tuberculosis?

A) 20%
B) 36%
C) 45%
D) 54%
E) 80%

We can divide the students into the following 4 groups (with the variables denoting the number in each):

1) ≥ 20 years of age and susceptible to tuberculosis = a

2) ≥ 20 years of age and not susceptible to tuberculosis = b

3) < 20 years of age and susceptible to tuberculosis = c

4) < 20 years of age and not susceptible to tuberculosis = d

We are given that 0.1(a + c) = c and 0.4(b + d) = b and 0.09(a + b + c + d) = a. We need to find b/(a + b).

Multiplying the first equation by 10, we have a + c = 10c → a = 9c → c = a/9.

Multiplying the second equation by 5, we have 2b + 2d = 5b → 2d = 3b → d = 3b/2.

Multiplying the third equation by 100, we have 9a + 9b + 9c + 9d = 100a. Substituting c = a/9 and d = 3b/2, we have:

9a + 9b + 9(a/9) + 9(3b/2) = 100a

9a + 9b + a + 27b/2 = 100a

18a + 18b + 2a + 27b = 200a

45b = 180a

b = 4a

So b/(a + b) = 4a/(a + 4a) = 4a/(5a) = 4/5 = 80%

_________________

GRE Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions Re: In a survey,it was found that 10% of the students who a   [#permalink] 28 May 2018, 18:22
Display posts from previous: Sort by

# Re: In a survey,it was found that 10% of the students who a  Question banks Downloads My Bookmarks Reviews Important topics Powered by phpBB © phpBB Group Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.