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Combinations

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axl_oz
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Combinations [#permalink] New post   05 Feb 2009, 18:48
Please see the attachment... Please explain the answer...



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Re: Combinations [#permalink] New post   05 Feb 2009, 19:46
axl_oz wrote:
Please see the attachment... Please explain the answer...



10C3*10C3
= 10*9*8/(1*2*3) *10*9*8/(1*2*3)
= 120*120 = 14400
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Re: Combinations [#permalink] New post   05 Feb 2009, 23:01
x2suresh, can you please explain your answer? Thanks!!!
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Re: Combinations [#permalink] New post   05 Feb 2009, 23:45
Ibodullo wrote:
x2suresh, can you please explain your answer? Thanks!!!


10 - Republicans
10 - Democrates

Answ= No of Ways choose 3 R out of 10 R * No of Ways choose 3 D out of 10 D
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Re: Combinations [#permalink] New post   06 Feb 2009, 10:28
x2suresh wrote:
Ibodullo wrote:
x2suresh, can you please explain your answer? Thanks!!!


10 - Republicans
10 - Democrates

Answ= No of Ways choose 3 R out of 10 R * No of Ways choose 3 D out of 10 D

why would be 10x9x8x10x9x8 wrong?
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x2suresh
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Re: Combinations [#permalink] New post   06 Feb 2009, 11:01
tusharvk wrote:
x2suresh wrote:
Ibodullo wrote:
x2suresh, can you please explain your answer? Thanks!!!


10 - Republicans
10 - Democrates

Answ= No of Ways choose 3 R out of 10 R * No of Ways choose 3 D out of 10 D

why would be 10x9x8x10x9x8 wrong?


You are using Permutations.. that's valid if order matters..

e.g. consider you have group of 3 repuplicans.. R1 R2 R3
how many ways you will select 2 Repulicans out of 3
Is it 3P2 or 3C2??? will see..

Your answer = 3P2 = 3*2 =6 ways
A1 A2 --A2 A1 <duplicate>
A2 A3 --A3 A2 <duplicate>
A3 A1 --A1 A3 <duplicate>

My answer = 3C2 = 3*2/2! = 3 ways.
A1 A2 =A2 A1
A2 A3 =A3 A2
A3 A1 =A1 A3




Did you get it
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Re: Combinations [#permalink] New post   06 Feb 2009, 12:08
axl_oz wrote:
Please see the attachment... Please explain the answer...


The question clearly says combination. so permutation doesnot aapply to this case.

No of ways the cgroup can be made = 10c3 x 10c3 = 14,400



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Re: Combinations [#permalink]
06 Feb 2009, 12:08
Moderator:
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

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