Just For Fun - Handshakes

[kuiperbelt]

https://ibb.co/zfXDgLt

[Hopkirk]

None because of covid, just elbow bumps.

[barry1010]

380

[JJ109]

20 people * 19 people / 2 = 190 handshakes

Each of the 20 people shake 19 hands - 380 hands shaken, but 2 hands are shaken in each handshake therefore divide by 2 = 190

[JJ109]

Another way of looking at it
1 shakes 19 hands and then leaves the room
next one shakes 18 hands and then leaves the room
next one shakes 17 hands andthen leaves the room
and so on
Therefore you need to sum 19 +18 + 17 ....+ 3 + 2 + 1
=(19 +1)* (19/2)
= 20 * 9.5
= 190

[ToraToraTora]

n/2*(n-1)=190

[barry1010]

I'm an idiot

[ToraToraTora]

don't put yourself down barry!

[barry1010]

Well it's so blerdy obvious

[kuiperbelt]

Barry thanks for your post. Your 'take' on the problem was interesting and happens to be correct when taking into account the number of hands involved (as shown by JJ109) in those handshakes. Again thankyou!!

[MissTerious2]

Are the two rows separated as in diagram?

[kuiperbelt]

As far as I know MissT2 there are just 20 people in a room. Am interested though in your 'take' on the problem if they are 2 separate rows of ten people :-)

[MissTerious2]

Actually, I immediately saw it as two rows of 1. Just show how different we all are and how sideways thinking comes into it

[MissTerious2]

Thanks for posting these. Keep up the good work!

[MissTerious2]

Two rows of 10, not 1