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

 It is currently 21 Jan 2019, 14:10

### 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

## Events & Promotions

###### Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
• ### GMAT Club Tests are Free & Open for Martin Luther King Jr.'s Birthday!

January 21, 2019

January 21, 2019

10:00 PM PST

11:00 PM PST

Mark your calendars - All GMAT Club Tests are free and open January 21st for celebrate Martin Luther King Jr.'s Birthday.
• ### The winners of the GMAT game show

January 22, 2019

January 22, 2019

10:00 PM PST

11:00 PM PST

In case you didn’t notice, we recently held the 1st ever GMAT game show and it was awesome! See who won a full GMAT course, and register to the next one.

# At a certain medical conference, there are only doctors and nurses. If

Author Message
TAGS:

### Hide Tags

Senior DS Moderator
Joined: 27 Oct 2017
Posts: 1199
Location: India
GPA: 3.64
WE: Business Development (Energy and Utilities)
At a certain medical conference, there are only doctors and nurses. If  [#permalink]

### Show Tags

03 Nov 2018, 09:16
1
4
00:00

Difficulty:

85% (hard)

Question Stats:

35% (01:45) correct 65% (01:24) wrong based on 51 sessions

### HideShow timer Statistics

At a certain medical conference, there are only doctors and nurses. If 4 people are to be randomly chosen from the conference attendees, what is the probability of randomly choosing at least n doctor(s)?
1) The probability of randomly selecting 4 nurses is $$\frac{1}{3}$$
2) n = 1

Weekly Quant Quiz #7 Question No 8

_________________
Manager
Joined: 04 Jun 2018
Posts: 127
Re: At a certain medical conference, there are only doctors and nurses. If  [#permalink]

### Show Tags

03 Nov 2018, 09:46
1
At a certain medical conference, there are only doctors and nurses. If 4 people are to be randomly chosen from the conference attendees, what is the probability of randomly choosing at least n doctor(s)?
1) The probability of randomly selecting 4 nurses is 1/3
2) n = 1

We don't know the value of n or the total number of D and N.

1.
Probablity is:
NC4/D+NC4=0.33

Since we dont know the value of n. Clearly NS(N=1,2,3)

2.
N=1.
NS.

Combining:
Atleast 1= 1- prob all nurses

1- NC4/D+NC4
Hence,
1-0.33= 66.67

Hence combing C ans
Manager
Joined: 16 Sep 2011
Posts: 93
Re: At a certain medical conference, there are only doctors and nurses. If  [#permalink]

### Show Tags

03 Nov 2018, 09:49
At a certain medical conference, there are only doctors and nurses. If 4 people are to be randomly chosen from the conference attendees, what is the probability of randomly choosing at least n doctor(s)?
1) The probability of randomly selecting 4 nurses is 1/3
2) n = 1

Option A: 4 nurses prob = 1/3, so rest is (combination of nurse + doctor or only doctor) = 2/3 . Moreover 1/3 does say that there are total 12 people comprising of nurse and doctor ....we also do not know how many doctors are there in 12 (may be 1, or 2 or 8 max)

now prob of selecting n doctor so it can be 1 doctor , 2 , 3 or 4.... accordingly prob will be different

so A is not sufficient

Option B: n = 1....so we need only 1 doctor but number of people , doctor or nurse we do not know..population size is also not known

Option B is not sufficient

Lets combine A and B, still we can't say because 1 out of how many doctors we do not know as we do not proportion of nurse and doctor in team of 12...may be 4, 8 or 6,6, 3, 9

Intern
Joined: 06 Nov 2018
Posts: 2
At a certain medical conference, there are only doctors and nurses. If  [#permalink]

### Show Tags

15 Nov 2018, 00:41
Q: At a certain medical conference, there are only doctors and nurses. If 4 people are to be randomly chosen from the conference attendees, what is the probability of randomly choosing at least n doctor(s)?
1) The probability of randomly selecting 4 nurses is 13
1
3

2) n = 1

Solution:
A. Looking at 1.
p(all nurses) = 1/3
p(at least n doc) = cannot be determined from the given info since 'n' can be 0, 1, 2, 3, 4 => INSUFFICIENT.

B. Looking at 2.
n = 1. It doesn't provide any info on the number of doctors/nurses => Insufficient

C. Combining 1 & 2.
=> p(at least 1 doc) = 1- p(no docs)
=> p(at least 1 doc) = 1- p(all nurses)
=> p(at least n doc) = 1- 1/3 = 2/3 = 0.667 SUFFICIENT

At a certain medical conference, there are only doctors and nurses. If &nbs [#permalink] 15 Nov 2018, 00:41
Display posts from previous: Sort by