Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

It is currently 17 Jul 2019, 03:43

Close

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
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.

Close

Request Expert Reply

Confirm Cancel

A certain class consists of 8 students, including Kim. Each

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Manager
Manager
User avatar
Joined: 28 May 2009
Posts: 144
Location: United States
Concentration: Strategy, General Management
GMAT Date: 03-22-2013
GPA: 3.57
WE: Information Technology (Consulting)
GMAT ToolKit User
A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 04 Mar 2013, 10:19
4
10
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

70% (02:00) correct 30% (02:05) wrong based on 233 sessions

HideShow timer Statistics


A certain class consists of 8 students, including Kim. Each day, three tasks must be completed and are assigned as follows: one of the 8 students is selected at random to complete Task A, one of the remaining 7 students is selected at random to complete Task B, and one of the remaining six students is selected at random to complete Task C. What is the probability that Kim will be selected to complete one of the three tasks?

(A) \(\frac{1}{3}\)

(B) \(\frac{3}{8}\)

(C) \(\frac{1}{24}\)

(D) \(\frac{1}{336}\)

(E) \(\frac{1}{512}\)

_________________
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56268
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 04 Mar 2013, 11:46
9
9
megafan wrote:
A certain class consists of 8 students, including Kim. Each day, three tasks must be completed and are assigned as follows: one of the 8 students is selected at random to complete Task A, one of the remaining 7 students is selected at random to complete Task B, and one of the remaining six students is selected at random to complete Task C. What is the probability that Kim will be selected to complete one of the three tasks?

(A) \(\frac{1}{3}\)

(B) \(\frac{3}{8}\)

(C) \(\frac{1}{24}\)

(D) \(\frac{1}{336}\)

(E) \(\frac{1}{512}\)


30-second approach: consider these 8 students in a row. The 3 tasks will be assigned to the first 3 students. Now, what is the probability that Kim will be among the first 3 students? 3/8.

Answer: B.

Similar questions to practice:
a-certain-team-has-12-members-including-joey-a-three-131321.html
a-certain-television-show-has-15-sponsors-including-company-127423.html
a-medical-researcher-must-choose-one-of-14-patients-to-127396.html
a-certain-class-consists-of-8-students-including-kim-127730.html
a-certain-club-has-10-members-including-harry-one-of-the-134891.html
laura-has-a-deck-of-standard-playing-cards-with-13-of-the-86902.html

Hope it helps.
_________________
General Discussion
SVP
SVP
User avatar
G
Status: Top MBA Admissions Consultant
Joined: 24 Jul 2011
Posts: 1790
GMAT 1: 780 Q51 V48
GRE 1: Q800 V740
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 04 Mar 2013, 10:41
2
1
Number of ways to select three students to complete the three tasks as described = 8C1 x 7C1 x 6C1 = 8 x 7 x 6

Number of ways to select the three students to complete the three tasks as described such that Kim is selected to do at least one = 7 x 6 + 7 x 6 + 7 x 6 = 7 x 6 x 3
[Here is the logic: If Kim is to do the first task, select the second student in 7C1 ways, and the third in 6C1 ways. If Kim is to do the second task, select a student to the first in 7C1 ways and a student to do the third in 6C1 ways. Similarly for the third task]

Therefore probability = (7x6x3)/(8x7x6) = 3/8

Option B
_________________
GyanOne [www.gyanone.com]| Premium MBA and MiM Admissions Consulting

Awesome Work | Honest Advise | Outstanding Results

Reach Out, Lets chat!
Email: info at gyanone dot com | +91 98998 31738 | Skype: gyanone.services
Manager
Manager
avatar
Joined: 08 Dec 2012
Posts: 61
Location: United Kingdom
WE: Engineering (Consulting)
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 11 Mar 2013, 13:30
1
1
Since the question is asking find the probability of completing one of the three task:
Probability of Kim doing task A = 1/8
Probability of Kim doing task B = 1/8
Probability of Kim doing task C = 1/8

So the probability of Kim doing one of the three tasks = 1/8 + 1/8 + 1/8 = 3/8
Answer B

Note: we are not using 1/7 and 1/6 as probability for tasks B and C because it is not specified it has to go in order of A, B and C.

Hope this makes sense
Manager
Manager
avatar
Joined: 02 Sep 2012
Posts: 201
Location: United States
Concentration: Entrepreneurship, Finance
GMAT Date: 07-25-2013
GPA: 3.83
WE: Architecture (Computer Hardware)
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 23 May 2013, 21:46
2
1
The question asks:
probability that Kim will be selected to complete one of the three tasks which is equal to1-( the probability that kim wil not be selected in any of the three tasks)
1-(7/8x6/7x5/6)=3/8

Is my approach on the problem correct?Can someone please clarify it?
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56268
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 24 May 2013, 01:20
Intern
Intern
avatar
Joined: 05 Mar 2012
Posts: 2
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 25 May 2013, 04:43
skamal7 wrote:
The question asks:
probability that Kim will be selected to complete one of the three tasks which is equal to1-( the probability that kim wil not be selected in any of the three tasks)
1-(7/8x6/7x5/6)=3/8

Is my approach on the problem correct?Can someone please clarify it?

sure, a smart approach.
it can be explained as follows
probability of A -1/8
probability of B - non ocurrence of A & Occurrence of B-7/8*1/7=1/8
probability of C 7/8*6/7*1/6=1/8
probability of A or B or C =1/8+1/8+1/8=3/8
Target Test Prep Representative
User avatar
D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 6923
Location: United States (CA)
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 12 Apr 2017, 12:03
1
1
megafan wrote:
A certain class consists of 8 students, including Kim. Each day, three tasks must be completed and are assigned as follows: one of the 8 students is selected at random to complete Task A, one of the remaining 7 students is selected at random to complete Task B, and one of the remaining six students is selected at random to complete Task C. What is the probability that Kim will be selected to complete one of the three tasks?

(A) \(\frac{1}{3}\)

(B) \(\frac{3}{8}\)

(C) \(\frac{1}{24}\)

(D) \(\frac{1}{336}\)

(E) \(\frac{1}{512}\)


The probability that Kim will be selected to complete one of the three tasks = P(Kim will be selected for task A) + P(Kim will be selected for task B) + P(Kim will be selected for task C)

Let’s calculate the probability that Kim will be selected for task A:

P(Kim will be selected for task A) = 1/8

Next, we calculate the probability that Kim will be selected for task B (i.e., she won’t be selected for task A):

P(Kim will be selected for task B) = P(Kim won’t be selected for task A) x P(Kim will be selected for task B) = 7/8 x 1/7 = 1/8

Finally, let’s calculate the probability that Kim will be selected for task C (i.e., she won’t be selected for either task A or task B):

P(Kim will be selected for task C) = P(Kim won’t be selected for task A) x P(Kim won’t be selected for task B) x P(Kim will be selected for task C) = 7/8 x 6/7 x 1/6 = 1/8

Thus, the probability that Kim will be selected for one of the three tasks is ⅛ + ⅛ + ⅛ = ⅜.

Alternate Solution:

We will use the fact that

P(Kim will be selected for one of the three tasks) + P(Kim will not be selected for any tasks) = 1

To calculate P(Kim will not be selected for any tasks), we note that this event happens if Kim is not selected for task A, B or C. Since there is a 1/8 probability that Kim is selected for task A, the probability that she is not selected for task A is 1 - 1/8 = 7/8. Similarly, the probability that she is not selected for tasks B and C are 6/7 and 5/6, respectively. Thus, the probability that she is not selected for any tasks is 7/8 x 6/7 x 5/6 = 5/8.

Now, since P(Kim will be selected for one of the three tasks) = 1 - P(Kim will not be selected for any tasks) and since P(Kim will not be selected for any tasks) = 5/8, we conclude that P(Kim will be selected for one of the three tasks) = 1 - 5/8 = 3/8.

Answer: B
_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 11667
Re: A certain class consists of 8 students, including Kim. Each  [#permalink]

Show Tags

New post 15 Aug 2018, 13:31
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Bot
Re: A certain class consists of 8 students, including Kim. Each   [#permalink] 15 Aug 2018, 13:31
Display posts from previous: Sort by

A certain class consists of 8 students, including Kim. Each

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne