GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 23 Oct 2018, 02:41

### 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

# Of the 700 members of a certain organization, 120 are lawyers. Two mem

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50044
Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

16 Jul 2018, 21:02
1
7
00:00

Difficulty:

95% (hard)

Question Stats:

36% (01:46) correct 64% (02:01) wrong based on 132 sessions

### HideShow timer Statistics

Of the 700 members of a certain organization, 120 are lawyers. Two members of the organization will be selected at random. Which of the following is closest to the probability that neither of the members selected will be a lawyer?

A. 0.5
B. 0.6
C. 0.7
D. 0.8
E. 0.9

_________________
Manager
Joined: 13 Oct 2013
Posts: 133
Concentration: Strategy, Entrepreneurship
Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

16 Jul 2018, 21:45
Probability of selecting 2 lawyers

120/700* 120*700 =0.2(approx)

Now probability of neither of the members is a lawyer = 1- 0.2= 0.8 (approx)

Ans: D
_________________

---------------------------------------------------------------------------------------------
Kindly press +1 Kudos if my post helped you in any way

Math Expert
Joined: 02 Aug 2009
Posts: 6979
Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

16 Jul 2018, 22:39
1
sunita123 wrote:
Probability of selecting 2 lawyers

120/700* 120*700 =0.2(approx)

Now probability of neither of the members is a lawyer = 1- 0.2= 0.8 (approx)

Ans: D

Hi..
this is not the correct way..
1-P( both are lawyers) = P that both are not lawyer, so it will include when 1 of them is a lawyer... so wrong

here we are looking for NEITHER is a lawyer, so both are NOT lawyer, so 580C2
P = $$\frac{580}{700}*\frac{579}{699}$$~$$(\frac{580}{700})^2=(\frac{560+20}{700})^2=(0.8+0.03)^2=0.83^2=$$ something more than 0.65 so answer 0.7
C
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Director
Status: Learning stage
Joined: 01 Oct 2017
Posts: 908
WE: Supply Chain Management (Energy and Utilities)
Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

17 Jul 2018, 00:40
Bunuel wrote:
Of the 700 members of a certain organization, 120 are lawyers. Two members of the organization will be selected at random. Which of the following is closest to the probability that neither of the members selected will be a lawyer?

A. 0.5
B. 0.6
C. 0.7
D. 0.8
E. 0.9

P(neither lawyer)=$$\frac{Ways-of-selecting-both-non-Lawyers}{Ways-of-selecting-2-members-out--of-700-members}$$
=$$\frac{580C2}{700C2}$$
=0.68
0.68 can be approximated to 0.7.

Ans. (C)
_________________

Regards,

PKN

Rise above the storm, you will find the sunshine

Director
Joined: 31 Oct 2013
Posts: 652
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

17 Jul 2018, 08:12
Bunuel wrote:
Of the 700 members of a certain organization, 120 are lawyers. Two members of the organization will be selected at random. Which of the following is closest to the probability that neither of the members selected will be a lawyer?

A. 0.5
B. 0.6
C. 0.7
D. 0.8
E. 0.9

Note : we are asked to determine the probability of members who are not lawyer.

Total case : 700C2

Probable event = (700 - 120 ) = 580C2

Probability = 580C2 / 700C2

= 0.68 ~ 0.7.

Director
Joined: 14 Dec 2017
Posts: 504
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

17 Jul 2018, 21:50
Bunuel wrote:
Of the 700 members of a certain organization, 120 are lawyers. Two members of the organization will be selected at random. Which of the following is closest to the probability that neither of the members selected will be a lawyer?

A. 0.5
B. 0.6
C. 0.7
D. 0.8
E. 0.9

# of non lawyers = 700 - 120 = 580

Probability of selecting 2 non lawyers = (580/700)*(579/699) =~ (580/700)*(580/700) =0.6889 =~0.7

Thanks,
GyM
_________________
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3906
Location: United States (CA)
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

19 Jul 2018, 17:04
1
Bunuel wrote:
Of the 700 members of a certain organization, 120 are lawyers. Two members of the organization will be selected at random. Which of the following is closest to the probability that neither of the members selected will be a lawyer?

A. 0.5
B. 0.6
C. 0.7
D. 0.8
E. 0.9

Since 580 are not lawyers, the probability of selecting two members, neither of whom are lawyers, is:

580/700 x 579/699

Notice that the second fraction is approximately 580/700, so we can approximate the probability as:

580/700 x 580/700 = 58/70 x 58/70 = 29/35 x 29/35 ≈ 30/35 x 30/35 = 6/7 x 6/7 = 36/49 ≈ 36/50 = 0.72
Of the numbers in the given choices, the closest to this is 0.7.

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Intern
Joined: 04 May 2014
Posts: 45
Concentration: Strategy, Operations
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

02 Aug 2018, 02:12
sunita123 wrote:
Probability of selecting 2 lawyers

120/700* 120*700 =0.2(approx) <----- The multiplication is wrong. It will be 0.02 instead of 0.2

Now probability of neither of the members is a lawyer = 1- 0.2= 0.8 (approx)

Ans: D
Intern
Joined: 04 May 2014
Posts: 45
Concentration: Strategy, Operations
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

02 Aug 2018, 02:18
chetan2u wrote:
sunita123 wrote:
Probability of selecting 2 lawyers

120/700* 120*700 =0.2(approx)

Now probability of neither of the members is a lawyer = 1- 0.2= 0.8 (approx)

Ans: D

Hi..
this is not the correct way..
1-P( both are lawyers) = P that both are not lawyer, so it will include when 1 of them is a lawyer... so wrong

here we are looking for NEITHER is a lawyer, so both are NOT lawyer, so 580C2
P = $$\frac{580}{700}*\frac{579}{699}$$~$$(\frac{580}{700})^2=(\frac{560+20}{700})^2=(0.8+0.03)^2=0.83^2=$$ something more than 0.65 so answer 0.7
C

Sir,
Can you please help me in removing my concept gap. I tried to solve it in a very layman way.
* Select one person from 580 and second person from 579
=(1/580) x (1/579)
Manager
Joined: 06 Nov 2016
Posts: 61
Location: Viet Nam
GPA: 3.54
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

02 Aug 2018, 10:06
1
tatz wrote:
chetan2u wrote:
sunita123 wrote:
Probability of selecting 2 lawyers

120/700* 120*700 =0.2(approx)

Now probability of neither of the members is a lawyer = 1- 0.2= 0.8 (approx)

Ans: D

Hi..
this is not the correct way..
1-P( both are lawyers) = P that both are not lawyer, so it will include when 1 of them is a lawyer... so wrong

here we are looking for NEITHER is a lawyer, so both are NOT lawyer, so 580C2
P = $$\frac{580}{700}*\frac{579}{699}$$~$$(\frac{580}{700})^2=(\frac{560+20}{700})^2=(0.8+0.03)^2=0.83^2=$$ something more than 0.65 so answer 0.7
C

Sir,
Can you please help me in removing my concept gap. I tried to solve it in a very layman way.
* Select one person from 580 and second person from 579
=(1/580) x (1/579)

This is not correct way to solve this question.
Since you mention "select one person from 580 ...", you can think it this way:

ways of selecting 1st member from 580 members who are not lawyers = 580C1 = 580
ways of selecting 2nd member from 579 members who are not lawyers = 579C1 = 579
Total possible ways = 700 (ways of selecting 1st member from 700 members) * 699 (ways of selecting 2nd member from the rest 699 members)

Therefore, Probability of selecting both members who are not lawyer = (580*579) / (700*699) = 0.7 (approx.)

Hope it helps.
_________________
Intern
Joined: 04 May 2014
Posts: 45
Concentration: Strategy, Operations
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem  [#permalink]

### Show Tags

02 Aug 2018, 13:29
Thanks Izzyjust5.. it made things clear ..
Probably selecting 1 object out of 580 objects (1/580) will be correct only when all objects are same/similar like all are red balls or green pens.
In case all objects are unique, we need to use combinations.. "r objects can be selected from a set of n unique objects in nCr ways.."
Re: Of the 700 members of a certain organization, 120 are lawyers. Two mem &nbs [#permalink] 02 Aug 2018, 13:29
Display posts from previous: Sort by