Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 27 May 2017, 22:12

### 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

# PS - Good probablity question

Author Message
Manager
Joined: 02 Aug 2007
Posts: 230
Schools: Life
Followers: 3

Kudos [?]: 61 [0], given: 0

PS - Good probablity question [#permalink]

### Show Tags

17 Jun 2008, 10:32
1
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Tricky question, thought I'd share with the group. Took me 3 mins to solve

A fair, six-sided die, with sides numbered one through six, is rolled 5 times. What is the probability that on exactly 3 rolls the number of dots showing is greater than 4?
A) 1/243
B) 10/243
C) 1/27
D) 40/243
E) 80/243

edit:
I mistyped, it should say "What is the probability that on exactly..."

Last edited by xALIx on 17 Jun 2008, 16:02, edited 2 times in total.
SVP
Joined: 30 Apr 2008
Posts: 1874
Location: Oklahoma City
Schools: Hard Knocks
Followers: 42

Kudos [?]: 590 [0], given: 32

Re: PS - Good probablity question [#permalink]

### Show Tags

17 Jun 2008, 10:53
Please rephrase the question. It's too confusing to be able to answer properly.
_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a.

GMAT Club Premium Membership - big benefits and savings

Current Student
Joined: 12 Jun 2008
Posts: 287
Schools: INSEAD Class of July '10
Followers: 8

Kudos [?]: 56 [1] , given: 0

Re: PS - Good probablity question [#permalink]

### Show Tags

17 Jun 2008, 11:09
1
KUDOS

In order to have more than 4 on exactly 3 rolls, you have to get 5 or 6 on 3 rolls (chance this happens for 1 roll: 2/6) and 1,2,3 or 4 on the 2 others (chance this happens for 1 roll: 4/6).

Once you chose which of the 3 rolls will bear the 5 or 6, you have (2/6)^3 * (4/6)^2 chances it happens

This is 4/243

And there are 10 choices of the 3 rolls on 5 (unordered choices).

CEO
Joined: 17 Nov 2007
Posts: 3586
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 575

Kudos [?]: 3982 [0], given: 360

Re: PS - Good probablity question [#permalink]

### Show Tags

17 Jun 2008, 11:24
Agree with Oski

$$p=C^5_3*(\frac{2}{6})^3*(\frac{4}{6})^2=\frac{5!*2^2}{3!*2!*3^5}=\frac{40}{243}$$
_________________

HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame

Manager
Joined: 02 Aug 2007
Posts: 230
Schools: Life
Followers: 3

Kudos [?]: 61 [0], given: 0

Re: PS - Good probablity question [#permalink]

### Show Tags

17 Jun 2008, 16:04
x-ALI-x wrote:
Tricky question, thought I'd share with the group. Took me 3 mins to solve

A fair, six-sided die, with sides numbered one through six, is rolled 5 times. What is the probability that on exactly 3 rolls the number of dots showing is greater than 4?
A) 1/243
B) 10/243
C) 1/27
D) 40/243
E) 80/243

edit:
I mistyped, it should say "What is the probability that on exactly..."

For this question, the answer is 40/243, the key is including the combinations so 4/243*10
Manager
Joined: 02 Aug 2007
Posts: 230
Schools: Life
Followers: 3

Kudos [?]: 61 [0], given: 0

Re: PS - Good probablity question [#permalink]

### Show Tags

17 Jun 2008, 16:05
I'll state the question differently, for similar practice:

A fair, six-sided die, with sides numbered one through six, is rolled 5 times. What is the probability that on exactly 3 rolls the number of dots showing is no greater than 4?
A) 1/243
B) 10/243
C) 1/27
D) 40/243
E) 80/243

btw, the answer is different from the one above
Current Student
Joined: 12 Jun 2008
Posts: 287
Schools: INSEAD Class of July '10
Followers: 8

Kudos [?]: 56 [0], given: 0

Re: PS - Good probablity question [#permalink]

### Show Tags

18 Jun 2008, 00:46
Same reasoning gives :
$$p=C^5_3*(\frac{4}{6})^3*(\frac{2}{6})^2=\frac{5!}{3!*2!}*\frac{2^3}{3^5}=\frac{80}{243}$$
Re: PS - Good probablity question   [#permalink] 18 Jun 2008, 00:46
Display posts from previous: Sort by