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# How many different ways can a group of 6 people be divided into 3 team

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Math Expert
Joined: 02 Sep 2009
Posts: 47898
How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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02 Jun 2016, 04:32
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How many different ways can a group of 6 people be divided into 3 teams of 2 people each?

(A) 4
(B) 9
(C) 15
(D) 24
(E) 36

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Math Expert
Joined: 02 Aug 2009
Posts: 6509
Re: How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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02 Jun 2016, 06:50
1
1
Bunuel wrote:
How many different ways can a group of 6 people be divided into 3 teams of 2 people each?

(A) 4
(B) 9
(C) 15
(D) 24
(E) 36
...

Hi,

1) 2 people can be choosen in 6C2 ways from 6 people = $$6C2=\frac{6!}{4!2!}= 15$$..
2) further 2 can be selected in 4C2 ways from remaining 4 people = $$4C2 = \frac{4!}{2!2!}= 6$$..
3) finally remaining 2 can be selected in 1 way..

Total ways = $$15*6*1 = 90$$ways..

But in these groups repetitions are there....
example - let them be a,b,c,d,e,f...
let a,b be selected in step(1), c,d in step(2) and e,f in step (3)..
Now in another way.. a,b is selected in step(2), c,d in step (3) and e,f in step (3)

Both the above are same but treated as different ways..
so we require to divide our total by ways the groups can be placed = 3!

answer = $$\frac{90}{3!} = \frac{90}{15} = 6$$
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
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3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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02 Jun 2016, 20:45
chetan2u wrote:
Bunuel wrote:
How many different ways can a group of 6 people be divided into 3 teams of 2 people each?

(A) 4
(B) 9
(C) 15
(D) 24
(E) 36
...

Hi,

1) 2 people can be choosen in 6C2 ways from 6 people = $$6C2=\frac{6!}{4!2!}= 15$$..
2) further 2 can be selected in 4C2 ways from remaining 4 people = $$4C2 = \frac{4!}{2!2!}= 6$$..
3) finally remaining 2 can be selected in 1 way..

Total ways = $$15*6*1 = 90$$ways..

But in these groups repetitions are there....
example - let them be a,b,c,d,e,f...
let a,b be selected in step(1), c,d in step(2) and e,f in step (3)..
Now in another way.. a,b is selected in step(2), c,d in step (3) and e,f in step (3)

Both the above are same but treated as different ways..
so we require to divide our total by ways the groups can be placed = 3!

answer = $$\frac{90}{3!} = \frac{90}{15} = 6$$

I dont fully understand about the dividing by 3! part.

why not divide by 2!?

Can you explain further?
Math Expert
Joined: 02 Aug 2009
Posts: 6509
Re: How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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02 Jun 2016, 21:30
Aves wrote:
chetan2u wrote:
Bunuel wrote:
How many different ways can a group of 6 people be divided into 3 teams of 2 people each?

(A) 4
(B) 9
(C) 15
(D) 24
(E) 36
...

Hi,

1) 2 people can be choosen in 6C2 ways from 6 people = $$6C2=\frac{6!}{4!2!}= 15$$..
2) further 2 can be selected in 4C2 ways from remaining 4 people = $$4C2 = \frac{4!}{2!2!}= 6$$..
3) finally remaining 2 can be selected in 1 way..

Total ways = $$15*6*1 = 90$$ways..

But in these groups repetitions are there....
example - let them be a,b,c,d,e,f...
let a,b be selected in step(1), c,d in step(2) and e,f in step (3)..
Now in another way.. a,b is selected in step(2), c,d in step (3) and e,f in step (3)

Both the above are same but treated as different ways..
so we require to divide our total by ways the groups can be placed = 3!

answer = $$\frac{90}{3!} = \frac{90}{15} = 6$$

I dont fully understand about the dividing by 3! part.

why not divide by 2!?

Can you explain further?

In the Q mentioned by you, we are dividing in two teams so first a team could be selected in 10C5 or in 5C1..
so two place swhere it can be selected and that is why we divide by 2..

But here we are dividing by 3! because any particular team can be selected in 6C2 or 4C2 or 2C1...

say the members are abcdef...
We select in 6C2 = ab...........4C2 = cd..........2C1= ef....
in another case in 6C2 = ab...........4C2 = ef..........2C1= cd....
in another case in 6C2 = cd...........4C2 = ef..........2C1= ab....
in another case in 6C2 = cd...........4C2 = ab..........2C1= ef....
in another case in 6C2 = ef...........4C2 = ab..........2C1= cd....
in another case in 6C2 = ef...........4C2 = cd..........2C1= ab....

so the distribution is the same BUT it has been calculated as 6 different ways....
so we divide total by 6 or 3! ways..
so we divide by (# of groups)!
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Re: How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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02 Jun 2016, 23:11
Bunuel wrote:
How many different ways can a group of 6 people be divided into 3 teams of 2 people each?

(A) 4
(B) 9
(C) 15
(D) 24
(E) 36

I like to think of it in this way:

Make everyone stand in a straight line. The number of ways of doing this is 6!.

Now, first two people from the left make team A, next two make team B and last two make team C.
We have divided 6 people in three teams (A, B and C) and allocated spots to each member in his team (first person, second person). But the three teams are not distinctly named teams so you un-arrange by dividing by 3!.
Also each team doesn't have an arrangement of "first person and second person" so you un-arrange them by dividing by 2! for each team.

6!/(3!*2!*2!*2!) = 15

_________________

Karishma
Veritas Prep GMAT Instructor

Save up to $1,000 on GMAT prep through 8/20! Learn more here > GMAT self-study has never been more personalized or more fun. Try ORION Free! Intern Joined: 06 Mar 2015 Posts: 27 Re: How many different ways can a group of 6 people be divided into 3 team [#permalink] ### Show Tags 03 Jun 2016, 07:00 chetan2u wrote: Bunuel wrote: How many different ways can a group of 6 people be divided into 3 teams of 2 people each? (A) 4 (B) 9 (C) 15 (D) 24 (E) 36 ... Hi, 1) 2 people can be choosen in 6C2 ways from 6 people = $$6C2=\frac{6!}{4!2!}= 15$$.. 2) further 2 can be selected in 4C2 ways from remaining 4 people = $$4C2 = \frac{4!}{2!2!}= 6$$.. 3) finally remaining 2 can be selected in 1 way.. Total ways = $$15*6*1 = 90$$ways.. But in these groups repetitions are there.... example - let them be a,b,c,d,e,f... let a,b be selected in step(1), c,d in step(2) and e,f in step (3).. Now in another way.. a,b is selected in step(2), c,d in step (3) and e,f in step (3) Both the above are same but treated as different ways.. so we require to divide our total by ways the groups can be placed = 3! answer = $$\frac{90}{3!} = \frac{90}{15} = 6$$ Hi, I understand that 6 people need to be divided into teams of 2 each. And as it is a team, the arrangement inside should make no difference at all. Hence 6C2 - 6*5/2 = 15 teams. I can't understand as to why you are again considering "4C2 ways from the remaining people". I guess am missing something monumental here, but i just can't get it. Is the logic that out of 6 people after forming teams of 2 people, you are still left with 4 people and hence can form teams of 2 again. This is my guess but i can't understand how can you consider that, as once you have divided them into 15 teams, you are left with nothing to re-divide? Math Expert Joined: 02 Aug 2009 Posts: 6509 Re: How many different ways can a group of 6 people be divided into 3 team [#permalink] ### Show Tags 03 Jun 2016, 07:28 nishi999 wrote: chetan2u wrote: Bunuel wrote: How many different ways can a group of 6 people be divided into 3 teams of 2 people each? (A) 4 (B) 9 (C) 15 (D) 24 (E) 36 ... Hi, 1) 2 people can be choosen in 6C2 ways from 6 people = $$6C2=\frac{6!}{4!2!}= 15$$.. 2) further 2 can be selected in 4C2 ways from remaining 4 people = $$4C2 = \frac{4!}{2!2!}= 6$$.. 3) finally remaining 2 can be selected in 1 way.. Total ways = $$15*6*1 = 90$$ways.. But in these groups repetitions are there.... example - let them be a,b,c,d,e,f... let a,b be selected in step(1), c,d in step(2) and e,f in step (3).. Now in another way.. a,b is selected in step(2), c,d in step (3) and e,f in step (3) Both the above are same but treated as different ways.. so we require to divide our total by ways the groups can be placed = 3! answer = $$\frac{90}{3!} = \frac{90}{15} = 6$$ Hi, I understand that 6 people need to be divided into teams of 2 each. And as it is a team, the arrangement inside should make no difference at all. Hence 6C2 - 6*5/2 = 15 teams. I can't understand as to why you are again considering "4C2 ways from the remaining people". I guess am missing something monumental here, but i just can't get it. Is the logic that out of 6 people after forming teams of 2 people, you are still left with 4 people and hence can form teams of 2 again. This is my guess but i can't understand how can you consider that, as once you have divided them into 15 teams, you are left with nothing to re-divide? Hi, if the Q said that we have to choose two people out of 6, then the answer would be straight 6C2.. But here we are talking of 3 teams of 2 each that is why we select 2 out of 6, then another 2 out of remaining 4 and then take remaining 2 as a team.. so these three 6C2, 4C2 and reamining 2, form a set of 3 teams of 2 players each.. Here since order does not matter, we divide it by 3!, so the answer finally comes same as 6C2.... _________________ 1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372 2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html 3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html GMAT online Tutor Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 8184 Location: Pune, India Re: How many different ways can a group of 6 people be divided into 3 team [#permalink] ### Show Tags 05 Jun 2016, 21:42 nishi999 wrote: I understand that 6 people need to be divided into teams of 2 each. And as it is a team, the arrangement inside should make no difference at all. Hence 6C2 - 6*5/2 = 15 teams. I can't understand as to why you are again considering "4C2 ways from the remaining people". I guess am missing something monumental here, but i just can't get it. Is the logic that out of 6 people after forming teams of 2 people, you are still left with 4 people and hence can form teams of 2 again. This is my guess but i can't understand how can you consider that, as once you have divided them into 15 teams, you are left with nothing to re-divide? From your question I am guessing that you are confusing combinations with permutations. 6C2 is combination which is "only selection". Out of 6 people you select 2 in 15 ways. You do not arrange anyone. You have 6 people: A, B, C, D, E, F You can select two in 15 ways: 1. A, B 2. A, C 3. A, D ... ... 15. E, F You do nothing with the leftover 4 people. So in the next step, you select 2 more out of the 4 remaining to make another team. Finally, you are left with 2 people which make the third team. _________________ Karishma Veritas Prep GMAT Instructor Save up to$1,000 on GMAT prep through 8/20! Learn more here >

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Re: How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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05 Jun 2016, 22:41
1. The number of ways in which mn different items can be divided equally into m groups, each containing n objects and the order of the groups is not important is (mn)!/ (n!^ m )* m!

2. The number of ways in which mn different items can be divided equally into m groups, each containing n objects and the order of the groups is important is (mn)!/ (n!^ m )

Here order is not important so we have to divide and we apply formula 1
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Re: How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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18 Dec 2017, 22:42
Top Contributor
chetan2u wrote:
Bunuel wrote:
How many different ways can a group of 6 people be divided into 3 teams of 2 people each?

(A) 4
(B) 9
(C) 15
(D) 24
(E) 36
...

Hi,

1) 2 people can be choosen in 6C2 ways from 6 people = $$6C2=\frac{6!}{4!2!}= 15$$..
2) further 2 can be selected in 4C2 ways from remaining 4 people = $$4C2 = \frac{4!}{2!2!}= 6$$..
3) finally remaining 2 can be selected in 1 way..

Total ways = $$15*6*1 = 90$$ways..

But in these groups repetitions are there....
example - let them be a,b,c,d,e,f...
let a,b be selected in step(1), c,d in step(2) and e,f in step (3)..
Now in another way.. a,b is selected in step(2), c,d in step (3) and e,f in step (3)

Both the above are same but treated as different ways..
so we require to divide our total by ways the groups can be placed = 3!

answer = $$\frac{90}{3!} = \frac{90}{15} = 6$$

_________________

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How many different ways can a group of 6 people be divided into 3 team  [#permalink]

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12 May 2018, 07:07
The smoothest way to solve this is by thinking it like this:

- We have 6 people (A, B, C, D, E, F) and we want 3 teams. Therefore we will have 3 2-member teams. The final teams will be for example: AB, CD, EF.
- Imagine a 6x6 table with A, B, C, D, E, F horizontally and vertically. Those are the possible 2-member teams.
- You need the half triangle without the mid-boxes. Meaning you don't want AA, BB, CC, DD, EE, FF and you don't want to double count AB and BA etc..
- Therefore 6*6=36. Minus the mid-boxes we have 30. And the bottom half we want is 15.
How many different ways can a group of 6 people be divided into 3 team &nbs [#permalink] 12 May 2018, 07:07
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