A radio station has to choose three days of the seven

Oldest

Best Reply

Author

Message

TAGS:

Magoosh GMAT Instructor

Joined: 28 Dec 2011

Posts: 858

Followers: 222

Kudos [?]: 618 [0], given: 14

A radio station has to choose three days of the seven [#permalink]

03 Dec 2012, 12:02

00:00

Question Stats:

85% (01:48) correct

14% (00:50) wrong

based on 14 sessions

A radio station has to choose three days of the seven in a week to broadcast a certain program, and that set will repeat each week. The program can be broadcast equally on any of the seven weekdays —- weekdays vs. weekends don’t matter at all —- nor does it matter whether the days the program airs are adjacent or not. Absolutely any three of the seven weekdays can be chosen. How many different three-day combinations of the seven weekdays can be constructed?
(A) 9
(B) 15
(C) 21
(D) 35
(E) 56

For tips on calculating the answer to questions like this without a calculator, see this post:
http://magoosh.com/gmat/2012/gmat-math- ... binations/
Experts, feel free to share you own non-calculator tips for calculating nCr values.

Mike :-)

[Reveal] Spoiler: OA

_________________

Mike McGarry
Magoosh Test Prep

Kaplan GMAT Prep Discount Codes

Knewton GMAT Discount Codes

Veritas Prep GMAT Discount Codes

Director

Status: Disappointed devil..

Joined: 15 Sep 2012

Posts: 591

Location: India

Concentration: Strategy, General Management

Schools: Ross '15 (D), Duke '15 (D), Johnson '15 (S), INSEAD Jan '14

WE: Information Technology (Computer Software)

Followers: 20

Kudos [?]: 230 [0], given: 23

Re: A radio station has to choose three days of the seven [#permalink]

04 Dec 2012, 00:59

mikemcgarry wrote:

Pick 3 days out of 7.. 7C3 = 7!/(4!*3!) = 35

Ans D it is.
_________________

Lets Kudos!!! ;-)
Black Friday Debrief
Most important component: Cast you vote

Senior Manager

Joined: 13 Aug 2012

Posts: 468

Followers: 13

Kudos [?]: 88 [0], given: 11

Re: A radio station has to choose three days of the seven [#permalink]

27 Dec 2012, 02:38

I used the ANAGRAM technique to answer this question:

D1 D2 D3 D4 D5 D6 D7
N N N Y Y Y N

ANAGRAM gets the permutation of the options and then divide it by the number of selected and the number of not selected. In our case, we are looking for the permutation of 7 days divided by 3 selections and 4 non-selections.

=\frac{7!}{4!3!}=7*5=35

Answer: D

Re: A radio station has to choose three days of the seven [#permalink] 27 Dec 2012, 02:38

		Similar topics	Author	Replies	Last post
Similar Topics:		Radio stations with radio data system (RDS) technology	ffgmat	12	25 May 2006, 11:52
		GMATPrep: Probability Radio stations.	M8	6	02 Jul 2006, 07:50
		Radio stations with radio data system (RDS) technology	quangviet512	5	22 Sep 2006, 09:05
		On his drive to work, Leo listens one of three radio station	shobuj40	2	12 Jan 2009, 06:22
	1	Radio Station	alexn49	3	11 Nov 2010, 08:00

A radio station has to choose three days of the seven

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

A radio station has to choose three days of the seven

A radio station has to choose three days of the seven

Main navigation

GMAT Resources

Partners

MBA Resources