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#1 2010-03-20 16:43:18
- soha
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- Registered: 2006-07-07
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In a function..
In a function people greet themselves with shake hands. If the number of shake hands is
4950, then people present there are ------
A) 120 B) 110 C) 100 D) 90
"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!" 
- David O. McKay
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#2 2010-03-20 18:23:45
- bobbym
- bumpkin
- From: Bumpkinland
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Re: In a function..
Hi soha;
C) 100
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#3 2010-03-21 02:40:08
- soha
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Re: In a function..
How did you get that ???? Please explain???
"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay
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#4 2010-03-21 10:00:11
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: In a function..
Hi soha;
The number of handshakes between n people is:
Solve for:
n = - 99 and n = 100 You can't have -99 people so n = 100
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#5 2010-03-21 19:57:44
- soha
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Re: In a function..
we get n^2 - n -9900 = 0
after this..??
"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay
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#6 2010-03-21 20:59:12
- ZHero
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Re: In a function..
Split the middle term (i.e. -n) as -100n and 99n and then factorize and equate to zero!
u'll get two values of n------->100 and -99.
If two or more thoughts intersect, there has to be a point!
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#7 2010-03-29 23:07:24
- soha
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Re: In a function..
Hi soha;
The number of handshakes between n people is:
how did you get this?
"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay
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#8 2010-03-29 23:45:05
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: In a function..
Hi soha;
Easiest way to understand this is the first person shakes 99 hands. The second person shakes 98 hands,The third person shakes 97 hands, the fourth person shakes 96 hands. until the 99th person, who only shakes the 100th hand . So there are
! + 2 + 3 + 4 + 5 + 6 + ... + 99 = 4950
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#9 2010-04-01 02:51:45
- soha
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- Posts: 2,530
Re: In a function..
Why do we take that the first person shakes 99 hands ????
i mean , why 99 ? Why not any other number?
"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay
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#10 2010-04-01 03:28:37
- ZHero
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Re: In a function..
Why do we take that the first person shakes 99 hands ????
i mean , why 99 ? Why not any other number?
hi!!!!
Let the no. of people be X.
Hence, 1st person will shake hand with everybody else except He Himself i.e. X-1 people!
2nd will shake hand with X-2 people (not X-1 coz he's already shook hand with 1st!)!
and so on....
Hence, total no. of hand shakes=X+(X-1)+(X-2)+.....+3+2+1=4950!
Bobbym was just showing u that X=100 is the Right Answer!!
If two or more thoughts intersect, there has to be a point!
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#11 2010-04-01 16:48:53
- soha
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Re: In a function..
x+ (x-1) +(x-2)+........... + 3+2+1=4950
how can we get x next ??
"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay
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#12 2010-04-01 21:07:06
- ZHero
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Re: In a function..
x+(x-1) +(x-2)+........... + 3+2+1=4950
how can we get x next ??
Sorry but in d above expression, first term X won't be there because first person shakes hand with X-1 people...
It shud be...
(X-1)+(X-2)+.......+3+2+1 which is the sum of first X-1 natural nos.
=
Hint:use formula for sum of X terms of an AP with first term 1 and Common Diff. 1.
Last edited by ZHero (2010-04-01 21:20:43)
If two or more thoughts intersect, there has to be a point!
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