It is currently 17 Oct 2017, 03:10

### 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 June
Open Detailed Calendar

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

Author Message
TAGS:

### Hide Tags

Manager
Joined: 28 May 2009
Posts: 155

Kudos [?]: 263 [4], given: 91

Location: United States
Concentration: Strategy, General Management
GMAT Date: 03-22-2013
GPA: 3.57
WE: Information Technology (Consulting)
A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

04 Mar 2013, 10:19
4
KUDOS
9
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

72% (01:33) correct 28% (01:49) wrong based on 200 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) $$\frac{1}{512}$$
[Reveal] Spoiler: OA

_________________

Kudos [?]: 263 [4], given: 91

VP
Joined: 24 Jul 2011
Posts: 1347

Kudos [?]: 641 [2], given: 20

GMAT 1: 780 Q51 V48
GRE 1: 1540 Q800 V740
Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

04 Mar 2013, 10:41
2
KUDOS
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 | Top MBA Rankings and MBA Admissions Blog

Premium MBA Essay Review|Best MBA Interview Preparation|Exclusive GMAT coaching

Get a FREE Detailed MBA Profile Evaluation | Call us now +91 98998 31738

Kudos [?]: 641 [2], given: 20

Math Expert
Joined: 02 Sep 2009
Posts: 41871

Kudos [?]: 128512 [8], given: 12179

Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

04 Mar 2013, 11:46
8
KUDOS
Expert's post
6
This post was
BOOKMARKED
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.

Similar questions to practice:
a-certain-team-has-12-members-including-joey-a-three-131321.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.
_________________

Kudos [?]: 128512 [8], given: 12179

Manager
Joined: 08 Dec 2012
Posts: 66

Kudos [?]: 269 [1], given: 31

Location: United Kingdom
WE: Engineering (Consulting)
Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

11 Mar 2013, 13:30
1
KUDOS
1
This post was
BOOKMARKED
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

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

Kudos [?]: 269 [1], given: 31

Manager
Joined: 02 Sep 2012
Posts: 245

Kudos [?]: 219 [2], given: 99

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

23 May 2013, 21:46
2
KUDOS
1
This post was
BOOKMARKED
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?
_________________

"Giving kudos" is a decent way to say "Thanks" and motivate contributors. Please use them, it won't cost you anything

Kudos [?]: 219 [2], given: 99

Math Expert
Joined: 02 Sep 2009
Posts: 41871

Kudos [?]: 128512 [0], given: 12179

Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

24 May 2013, 01:20
skamal7 wrote:
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?

Yes, that's correct.
_________________

Kudos [?]: 128512 [0], given: 12179

Intern
Joined: 05 Mar 2012
Posts: 4

Kudos [?]: [0], given: 24

Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

25 May 2013, 04:43
skamal7 wrote:
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

Kudos [?]: [0], given: 24

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16764

Kudos [?]: 273 [0], given: 0

Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

21 Jul 2014, 22:54
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.
_________________

Kudos [?]: 273 [0], given: 0

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16764

Kudos [?]: 273 [0], given: 0

Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

28 Aug 2015, 21:25
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.
_________________

Kudos [?]: 273 [0], given: 0

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16764

Kudos [?]: 273 [0], given: 0

Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

06 Apr 2017, 04:38
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.
_________________

Kudos [?]: 273 [0], given: 0

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 1619

Kudos [?]: 835 [1], given: 2

Location: United States (CA)
Re: A certain class consists of 8 students, including Kim. Each [#permalink]

### Show Tags

12 Apr 2017, 12:03
1
KUDOS
Expert's post
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.

_________________

Scott Woodbury-Stewart
Founder and CEO

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

Kudos [?]: 835 [1], given: 2

Re: A certain class consists of 8 students, including Kim. Each   [#permalink] 12 Apr 2017, 12:03
Display posts from previous: Sort by

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

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.