Please Help...Maths is hard.

Free Mind

Free Mind

I'm a Dragon! Rawr!
MBTI
INFJinity
My brain never seems to be able to get around such stupid things such as this.

When you have 25 people in a room and everyone shakes each other's hand, how many handshakes have taken place?

Can someone please figure it out and tell me how they did it? It's confuzzling me. I need explaining to in the most simplistic manor...
 
Wouldn't it just be 24^2? Because everyone will have shaken 24 different hands.
 
Maths need to die a horrible slow death. :m142:
 
It's a trick question. They said "how many handshakes will have taken place", not "how many handshakes will have taken place in a room where etc etc etc" so they could mean in all the world and parallel universes, not in the room with people shaking each others hands for no reason. Your teacher is obviously Satan.
 
Royal said:
It's a trick question. They said "how many handshakes will have taken place", not "how many handshakes will have taken place in a room where etc etc etc" so they could mean in all the world and parallel universes, not in the room with people shaking each others hands for no reason. Your teacher is obviously Satan.
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O________________o
 
Royal said:
It's a trick question. They said "how many handshakes will have taken place", not "how many handshakes will have taken place in a room where etc etc etc" so they could mean in all the world and parallel universes, not in the room with people shaking each others hands for no reason. Your teacher is obviously Satan.
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Free Mind said:
O________________o
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:m146:


haha sorry, couldn't help it.
 
25 people?

The first person will shake hands with 24 people; the next with the remaining 23, the third with the remaining 22, etc.

24+23+22+21+20+19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1 = 300

or

n/2 * n-1
ie. 25/2 * 24 = 300
 
Inevitably not everyone will shake everyone else's hand :p (Sorry wish I could give you a real answer but I'm no good at maths.)
 
Flavus Aquila said:
25 people?

The first person will shake hands with 24 people; the next with the remaining 23, the third with the remaining 22, etc.

24+23+22+21+20+19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1 = 300

or

n/2 * n-1
ie. 25/2 * 24 = 300
Click to expand...

Yeah...that's what I was going to say....

not.

(I would have thought 24 x 24...I have failed math many many times)
 
Flavus Aquila said:
25 people?

The first person will shake hands with 24 people; the next with the remaining 23, the third with the remaining 22, etc.

24+23+22+21+20+19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1 = 300

or

n/2 * n-1
ie. 25/2 * 24 = 300
Click to expand...

Ok, now I get it.

091128-derp.jpg
 
agree with [MENTION=862]Flavus Aquila[/MENTION] and [MENTION=1678]Norton[/MENTION]
n is 25
Everyone will shake everyone else's hand but they won't shake their own hands hence n-1 = 24
Since 2 people take part in 1 handshake the number of handshakes is half the product of n and n-1.
Therefore (n*(n-1))/2
Hope that makes the formula easier to understand.
 
Golly gosh, I really do suck at maths...It really isn't an INFJ's strong point is it? I may stick to hugs. :hug:

Thanks for helping out. REPS FOR ALL WHO COMMENT HERE!
 
Free Mind said:
Golly gosh, I really do suck at maths...It really isn't an INFJ's strong point is it?
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I don't think that mathematics ability, or lack thereof, has anything to do with personality. My INFJ wife, son and brother-in-law are all very good at mathematics. All of them are scientists (my son is an aspiring one). I'm convinced that the great Russian physicist and dissident, Andrei Sakharov, was an INFJ. Similarly, not all INTJ's and INTP's are necessarily good at mathematics. Everyone can become competent at mathematics, though, if they work at it. Do lots of problem sets, look for patterns and generalize. The problem of this thread is a classic example.
 
Flavus Aquila said:
25 people?

The first person will shake hands with 24 people; the next with the remaining 23, the third with the remaining 22, etc.

24+23+22+21+20+19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1 = 300

or

n/2 * n-1
ie. 25/2 * 24 = 300
Click to expand...
That is beyond nifty!
 
Norton said:
I don't think that mathematics ability, or lack thereof, has anything to do with personality. My INFJ wife, son and brother-in-law are all very good at mathematics. All of them are scientists (my son is an aspiring one). I'm convinced that the great Russian physicist and dissident, Andrei Sakharov, was an INFJ. Similarly, not all INTJ's and INTP's are necessarily good at mathematics. Everyone can become competent at mathematics, though, if they work at it. Do lots of problem sets, look for patterns and generalize. The problem of this thread is a classic example.
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Thanks for the advice. It's mainly due to my, why bother attitude towards math as I prefer doing other things. But really. I should try and get half decent at it to atleast have a simple understanding. I'm pretty pathetic. Thanks for the advice and helping me a bit. (:
 
Norton said:
I don't think that mathematics ability, or lack thereof, has anything to do with personality. My INFJ wife, son and brother-in-law are all very good at mathematics. All of them are scientists (my son is an aspiring one). I'm convinced that the great Russian physicist and dissident, Andrei Sakharov, was an INFJ. Similarly, not all INTJ's and INTP's are necessarily good at mathematics. Everyone can become competent at mathematics, though, if they work at it. Do lots of problem sets, look for patterns and generalize. The problem of this thread is a classic example.
Click to expand...

+1

Also, different teachers approach mathematics differently. Some kids learn very effectively with the rote method but others need to understand the "why", the underlying dynamics, the patterns as [MENTION=1678]Norton[/MENTION] said. Try reading different mathematics books to develop your own way of thinking about the problems.
 
Norton said:
Correct
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Damn, that's what I thought it was at first but then thought it was a double trick question and second guessed myself.

(n/2)x(n-1) is correct but i'm not sure why you divide by two. This is pretty much the useless part of math anyways. It's all about calculus, even though it can make you its b***h.
 
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