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.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

PS - Good probablity question [#permalink]
17 Jun 2008, 09:32

1

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

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

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, 15:02, edited 2 times in total.

Re: PS - Good probablity question [#permalink]
17 Jun 2008, 10:09

1

This post received KUDOS

I think answer is (D)

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).

Re: PS - Good probablity question [#permalink]
17 Jun 2008, 15:04

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

Re: PS - Good probablity question [#permalink]
17 Jun 2008, 15:05

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