Five friends met for lunch, and they all shook hands. Each person shook the other persons right hand only once. What was the total number of handshakes?
Five friends met for lunch, and they all shook hands. Each person shook the other persons right hand only once. What was the total number of handshakes?
Would you add 5+5?
No. Let A B C D E be the people. Then A shakes hands with B,C,D,E. Then B shakes hands with C,D,E but not A because they already shook hands. Then C shakes hands with D,E. And D shakes hands with only E.
I know you did but i really don't know what to do..do i just add up the letters? I still came up with 10.
Yes, 10 is the right answer. If you add up the lines. But your reasoning that 5+5=10 is wrong. Try for example 4 people instead of 5. Then the answer would be 3+2+1 = 6 and not 4 + 4 = 8.
If n people shake hands with each other such each pair of persons shake hands once and only once, the total number of handshakes is $\displaystyle ^n\mathrm{C}_2=\frac{n(n-1)}{2}$.