Question

There's 77 people in the party. Every person shakes hands with all the rest. How many handshakes will be traded?

Answer 1

Start counting with a first persons handshakes and work your way through all the persons, carefully not counting doubles.

Answer 2

76*77?

Answer 3

Nope.

Answer 4

How many handshakes is the first person involved in?

Answer 5

76

Answer 6

How many handshakes is the second person involved in that you haven't counted yet?

Answer 7

imagine them all standing in a line.
then the first person in the line leaves the line and shakes hands with how many people?
then the second person leaves the line and shakes hands with how many people?
carry on until the line is empty.

i.e. use the method Thomas9 outlined above.

Answer 8

So I should use sequence?

Answer 9

Nice visualisation, asnaseer.

Answer 10

exactly

Answer 11

thanks Thomas9

Answer 12

Thank you both!

Answer 13

yw