GMAT Changed on April 16th - Read about the latest changes here

It is currently 22 Apr 2018, 01:30

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

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

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

Hide Tags

Manager
Manager
User avatar
Status: Preparing for GMAT - March 2011
Joined: 21 May 2010
Posts: 126
Location: London
Schools: INSEAD, RSM, HEC, St. Gallen, IF, IESE
WE 1: Finance 6 years
A certain class consists of 8 students, including Don. Each [#permalink]

Show Tags

New post 01 Mar 2011, 04:39
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

65% (01:23) correct 35% (00:53) wrong based on 37 sessions

HideShow timer Statistics

A certain class consists of 8 students, including Don. 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 Don will be selected to complete one of the three tasks?

A. 1/3
B. 3/8
C. 1/24
D. 1/336
E. 1/512
[Reveal] Spoiler: OA

_________________

In The World Full Of Duplicates,, I Am The Only Masterpiece..
Girl Power
http://gmatclub.com/forum/beat-the-beast-with-non-native-speaker-108349.html

Math Forum Moderator
avatar
Joined: 20 Dec 2010
Posts: 1914
Re: word problem - Probability [#permalink]

Show Tags

New post 01 Mar 2011, 04:47
\(\frac{1}{8}*1*1 + \frac{7}{8}*\frac{1}{7}*1+\frac{7}{8}*\frac{6}{7}*\frac{1}{6}\)

\(3*\frac{1}{8} = \frac{3}{8}\)

Ans: "B"
_________________

~fluke

GMAT Club Premium Membership - big benefits and savings

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 44599
Re: word problem - Probability [#permalink]

Show Tags

New post 01 Mar 2011, 06:18
Expert's post
1
This post was
BOOKMARKED
tirupatibalaji wrote:
A certain class consists of 8 students, including Don. 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 Don will be selected to complete one of the three tasks?
(A) 1/3
(B) 3/8
(C) 1/24
(D) 1/336
(E) 1/512


Alternately you can find the probability that among 3 students chosen to complete the tasks won't be Don and subtract it from 1:
\(P=1-\frac{C^3_7}{C^3_8}=\frac{3}{8}\);

The same with probability approach: \(P=1-\frac{7}{8}*\frac{6}{7}*\frac{5}{6}=\frac{3}{8}\).

Answer: B.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

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.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Director
Director
avatar
Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing.
Affiliations: University of Chicago Booth School of Business
Joined: 03 Feb 2011
Posts: 813
Reviews Badge
Re: word problem - Probability [#permalink]

Show Tags

New post 01 Mar 2011, 06:21
P(don will not be selected to complete any) = (1 - 1/8) (1 - 1/7) (1 - 1/6) = 5/8

P(don will be selected atleast once) = 1 - 5/8 = 3/8
Expert Post
2 KUDOS received
GMAT Tutor
avatar
S
Joined: 24 Jun 2008
Posts: 1345
Re: word problem - Probability [#permalink]

Show Tags

New post 01 Mar 2011, 07:14
2
This post received
KUDOS
Expert's post
There's no need for a complicated solution here. We're selecting 3 people from 8 and we want to know the probability Don is selected. That's just like lining the 8 people up, and asking the probability Don is one of the first 3 people in line. There are 8 spots for Don, 3 of which are among the first three spots, so the probability must be 3/8.

edit - Or to look at it a different way, each of the 8 people is as likely as anyone else to be selected for A, for B, or for C. That is, the probability Don is selected for A is 1/8, for B is also 1/8 and for C is 1/8, so the probability he is selected for one of the three is 1/8 + 1/8 + 1/8 = 3/8.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 6645
Premium Member
Re: A certain class consists of 8 students, including Don. Each [#permalink]

Show Tags

New post 05 Apr 2018, 23:19
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 Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: A certain class consists of 8 students, including Don. Each   [#permalink] 05 Apr 2018, 23:19
Display posts from previous: Sort by

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

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


cron

GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.