Brain Teaser #1
First one to comment back with the correct answer wins!
You are at a party with 12 other guests. If every person at the party shakes hands with every other person at the party, how many hand shakes occur?
-minimix
posted by Woodlands Academy @ 16:18
6 Comments:
Sorry, that's not correct. Try again! MEOW!
Keep on trying! Maybe draw a picture to help you see what is happening. Good luck! Meow meow!!!
Still no correct answer. I wonder who will get this one right? Meow meow meow!!!
Still no correct answer. Hmmm. Really try drawing a picture.
For those that are wondering, the answer is 78. We worked it out in class. The first person shakes hands with 12 people. The second has already shaken hands with the first so only has 11 other hands to shake. This pattern continues so that it ends up being the following summation:
(n-1) for n = 2 to 13
Or simply 12 + 11 + 10 +...+1
Stay tuned for the next brain teaser!
Also,
I think of it has how many ways are there to choose a pair of people from a group of 13....
13c2 = 13!/(11!*2!) = 13*12/2 = 78
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