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Algebra

Blazing goIITian

 Joined: 25 Jul 2011 Post: 322
28 Mar 2012 13:11:09 IST
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8
439
P and C
Engineering Entrance , JEE Main , JEE Main & Advanced , Mathematics , Algebra

A total of $28$ handshakes was exchanged at the conclusion of a party. Assuming that each participant was equally polite toward all the others, the number of people present was:

$\textbf{(A)}\ 14 \qquad\textbf{(B)}\ 28 \qquad\textbf{(C)}\ 56 \qquad\textbf{(D)}\ 8 \qquad\textbf{(E)}\ 7$

Blazing goIITian

Joined: 21 Mar 2012
Posts: 1457
28 Mar 2012 13:15:28 IST
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a total of how many handshake

Hot goIITian

Joined: 10 Oct 2011
Posts: 120
28 Mar 2012 13:17:40 IST
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Blazing goIITian

Joined: 21 Mar 2012
Posts: 1457
28 Mar 2012 13:25:58 IST
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i cant see the whole question even not option will u write it again

Hot goIITian

Joined: 10 Oct 2011
Posts: 120
28 Mar 2012 13:33:05 IST
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hello tarun click answer on the right side bottom of the question then you can see the question  my friend :)

Blazing goIITian

Joined: 25 Jul 2011
Posts: 322
28 Mar 2012 13:51:01 IST
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@ Srini: Ur right machan !

$The number of handshakes with n people is \binom{n}{2} . Hence, n(n-1)/2=28 and n=8\Longrightarrow\mathrm{ (D) }$

Forum Expert
Joined: 19 Oct 2006
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28 Mar 2012 14:15:02 IST
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If the number of people are 'n' then

number of handshakes = (n-1) + (n-2) + (n-3)+ ...+1

or number of handshakes = n(n-1)/2

here number of handshakes = 28

So, n(n-1) / 2 = 28 on solving gives

n = 7

Blazing goIITian

Joined: 25 Jul 2011
Posts: 322
28 Mar 2012 17:54:18 IST
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@ edison sir: Sir,uve made an mistake in the last step sir...n=8 actually...

Blazing goIITian

Joined: 30 Aug 2011
Posts: 359
29 Mar 2012 21:45:34 IST
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yeah its 8

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