It is currently 24 Jun 2017, 16:09

### 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 test maker is to design a probability test from a list of

• 42% [3]
• 14% [1]
• 0% [0]
• 28% [2]
• 0% [0]
• 14% [1]
Author Message
TAGS:

### Hide Tags

Manager
Joined: 21 Jul 2009
Posts: 249
Location: New York, NY
A test maker is to design a probability test from a list of [#permalink]

### Show Tags

07 Oct 2009, 06:57
00:00

Difficulty:

(N/A)

Question Stats:

100% (01:21) correct 0% (00:00) wrong based on 12 sessions

### HideShow timer Statistics

A test maker is to design a probability test from a list of 21 questions. The 21 questions are classified into three categories: hard, intermediate and easy. If there are 7 questions in each category and the test maker is to select two questions from each category, how many different combinations of questions can the test maker put on the test?

A) 3*(7!/(5!2!))
B) 3*(7!/(5!))
C) 3*(7!/(2!))
D) 3*21
E) 72
Math Expert
Joined: 02 Sep 2009
Posts: 39662
Re: Test maker - combinations problem [#permalink]

### Show Tags

07 Oct 2009, 07:41
2
KUDOS
Expert's post
mendelay wrote:
A test maker is to design a probability test from a list of 21 questions. The 21 questions are classified into three categories: hard, intermediate and easy. If there are 7 questions in each category and the test maker is to select two questions from each category, how many different combinations of questions can the test maker put on the test?
A) 3*(7!/(5!2!))
B) 3*(7!/(5!))
C) 3*(7!/(2!))
D) 3*21
E) 72

There is no correct choice!

The number of combinations will be C(2,7)*C(2,7)*C(2,7)=C(2,7)^3=21^3=9261

Check the source. A and C give the same answers.
_________________
Manager
Joined: 21 Jul 2009
Posts: 249
Location: New York, NY
Re: Test maker - combinations problem [#permalink]

### Show Tags

07 Oct 2009, 07:59
The question is from PlatinumGmat http://www.platinumgmat.com/practice_gm ... on_id=2252
and the OA given there is A.

However, I disagree because 7C2*7C2*7C2 ≠ 37C2.
I think the answer is none of the above.
Math Expert
Joined: 02 Sep 2009
Posts: 39662
Re: Test maker - combinations problem [#permalink]

### Show Tags

07 Oct 2009, 08:05
1
KUDOS
Expert's post
mendelay wrote:
The question is from PlatinumGmat http://www.platinumgmat.com/practice_gm ... on_id=2252
and the OA given there is A.

However, I disagree because 7C2*7C2*7C2 ≠ 37C2.
I think the answer is none of the above.

They made a mistake: 7C2*7C2*7C2 ≠ 37C2 its (7C2)^3=9261. There must be a typo.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15951
Re: Test maker - combinations problem [#permalink]

### Show Tags

15 Nov 2013, 06:06
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.
_________________
Re: Test maker - combinations problem   [#permalink] 15 Nov 2013, 06:06
Similar topics Replies Last post
Similar
Topics:
1 Three competing juice makers conducted a blind taste test with mall 1 07 Apr 2016, 07:20
4 A certain list of 300 test scores has an arithmetic mean of 75 and a s 4 24 Dec 2016, 00:47
3 The list above shows the scores of 10 schoolchildren on a certain test 7 16 Oct 2016, 03:20
15 A certain list of 200 test scores has an average 16 26 Oct 2016, 00:11
A certain tests consists 8 sections with 25 questions, numbered from 3 12 Mar 2011, 02:57
Display posts from previous: Sort by

# A test maker is to design a probability test from a list of

 Powered by phpBB © phpBB Group and phpBB SEO 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®.