Combinations/Ratios question

This topic has expert replies
Source: — Problem Solving |

Legendary Member
Posts: 966
Joined: Sat Jan 02, 2010 8:06 am
Thanked: 230 times
Followed by:21 members

by shankar.ashwin » Wed Nov 02, 2011 7:32 am
5 people teams possible;

20C5 * 15C5 * 10C5 * 5C5 / 4!

4 people teams possible;

20C4 * 16C4 * 12C4 * 8C4 * 4C4 / 5!.

You need to find ratio between both.

User avatar
Community Manager
Posts: 1060
Joined: Fri May 13, 2011 6:46 am
Location: Utrecht, The Netherlands
Thanked: 318 times
Followed by:52 members

by neelgandham » Wed Nov 02, 2011 7:37 am
[spoiler]5/16 [/spoiler] ?
Anil Gandham
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/

Legendary Member
Posts: 966
Joined: Sat Jan 02, 2010 8:06 am
Thanked: 230 times
Followed by:21 members

by shankar.ashwin » Wed Nov 02, 2011 7:48 am
Is it just 20C5/20C4? I was assuming all 20 people be formed into teams of 5 and 4. That would be way too big a number..
neelgandham wrote:[spoiler]5/16 [/spoiler] ?

Newbie | Next Rank: 10 Posts
Posts: 8
Joined: Wed Nov 02, 2011 7:17 am

by frumpychic » Wed Nov 02, 2011 7:49 am
why is it not 20C4/20C5 ?
Last edited by frumpychic on Wed Nov 02, 2011 8:00 am, edited 1 time in total.

User avatar
GMAT Instructor
Posts: 349
Joined: Wed Sep 28, 2011 3:38 pm
Location: Austin, TX
Thanked: 236 times
Followed by:54 members
GMAT Score:770

by GmatMathPro » Wed Nov 02, 2011 7:53 am
I think it's 20C4/20C5=[spoiler]5/16[/spoiler]
Pete Ackley
GMAT Math Pro
Free Online Tutoring Trial

User avatar
Community Manager
Posts: 1060
Joined: Fri May 13, 2011 6:46 am
Location: Utrecht, The Netherlands
Thanked: 318 times
Followed by:52 members

by neelgandham » Wed Nov 02, 2011 8:01 am
shankar.ashwin wrote:Is it just 20C5/20C4? I was assuming all 20 people be formed into teams of 5 and 4. That would be way too big a number..
neelgandham wrote:[spoiler]5/16 [/spoiler] ?
I don't think the question asked the total number of ways in which 20 people can be arranged in 5 teams of 4 each. It just said 'different teams of 4'
Anil Gandham
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/