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In a random sample of 80 adults, how many are college

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In a random sample of 80 adults, how many are college [#permalink] New post 18 Sep 2012, 02:28
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The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

In a random sample of 80 adults, how many are college graduates?

(1) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates.
(2) In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates.

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Question: 44
Page: 278
Difficulty: 600


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Re: In a random sample of 80 adults, how many are college [#permalink] New post 18 Sep 2012, 02:29
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In a random sample of 80 adults, how many are college graduates?

(1) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates. Say the number of college graduates is x, then the number of not college graduates is 3x. Thus, x+3x=80. We can find x. Sufficient.

(2) In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates. Say the number of college graduates is x, then the number of not college graduates is x+(x+40). Thus, x+(x+40)=80. We can find x. Sufficient.

Answer: D.
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Re: In a random sample of 80 adults, how many are college [#permalink] New post 18 Sep 2012, 04:14
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Let the number of adults who are college graduates = x
& number of adults who are not college graduates = y
x+y = 80 ...(1)

1) y = 3x
Putting in equation (1), we get 4x= 80-----Sufficient
2) y = x + 40
Putting in equation (1), we get 2x + 40= 80-----Sufficient

Answer D
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Re: In a random sample of 80 adults, how many are college [#permalink] New post 18 Sep 2012, 05:39
Bunuel wrote:

In a random sample of 80 adults, how many are college graduates?

(1) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates.
(2) In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates.




Since there are 80 adults we don't need to consider non-adults number here. Otherwise, we would have to solve this by 2X2 matrix.
Either adults are college graduates (X) or not (Y)
Stmt 1) X + Y = 80
Y = 3X
these 2 eq can be solved to get the value of X

Stmt 2) Similar way
X + Y = 80
Y = 40 + X
these 2 eqns can also be solved for value of X

Both statements are sufficient, Hence D
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Re: In a random sample of 80 adults, how many are college [#permalink] New post 18 Sep 2012, 09:18
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

In a random sample of 80 adults, how many are college graduates?

(1) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates.
(2) In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates.

Practice Questions
Question: 44
Page: 278
Difficulty: 600


GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
1. Please provide your solutions to the questions;
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!


Lets say college going graduate is X
and college not going graduate is Y

form question X + Y = 80.
Option 1: Y = 3X
so, X + 3X = 80 leads to X = 20. Therefore option 1 is sufficient to answer the question.
Option 2: Y - X = 40.
so, 2Y = 120, leads to Y = 60 and X = 20. therefore option 2 is sufficient to anser the question.

Therefor from above both the options are individually sufficient to answer the question => "D" is the correct choice.
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Re: In a random sample of 80 adults, how many are college [#permalink] New post 19 Sep 2012, 23:30
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Total of 80 adults.
Let C be the college graduates.
let N be the non college grads.

What is C?

(1) N = 3C
3C + C = 80, SUFFICIENT.
(2) N = 40 + C
40 + C + C = 80, SUFFICIENT

answer: D
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Re: In a random sample of 80 adults, how many are college [#permalink] New post 21 Sep 2012, 03:10
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SOLUTION

In a random sample of 80 adults, how many are college graduates?

(1) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates. Say the number of college graduates is x, then the number of not college graduates is 3x. Thus, x+3x=80. We can find x. Sufficient.

(2) In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates. Say the number of college graduates is x, then the number of not college graduates is x+(x+40). Thus, x+(x+40)=80. We can find x. Sufficient.

Answer: D.

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COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: In a random sample of 80 adults, how many are college [#permalink] New post 10 Jan 2014, 07:16
Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

In a random sample of 80 adults, how many are college graduates?

(1) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates.
(2) In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates.

Practice Questions
Question: 44
Page: 278
Difficulty: 600


[textarea]GMAT Club is introducing a new project: The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project



Basically, we need to solve for x + y = 80, so we need to solve for 2 unknowns, either by solving for one of them or for both at the same time.

1) This statement tells us that x + 3x = 80, we have one equation and one unknown, so it's sufficient.
2) This tells us that (y + 40) + y = 80, so again we have 1 unknown and 1 equation, so we can solve it. Sufficient.

So we go with D.
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Re: In a random sample of 80 adults, how many are college [#permalink] New post 24 May 2014, 20:35
Rephrase the question
College = 80 - Non College
C = 80 - NC

i) In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates

3C + C = 80
4C = 80
C = 20

or

Part 1 3
Part 2 1
Ratio 4

80 = Ratio x 20

Non College = 60
College = 20

Sufficient - Linear equation with one variable

Statement II

NC = C + 40

C = 80 - C + 40
2C = 40
C = 20

Sufficient
Re: In a random sample of 80 adults, how many are college   [#permalink] 24 May 2014, 20:35
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