two people shake hands once. Three people shake hands three times.
i) How many times would 5 people shake hands
ii) Try and find a general formula.

Question

two people shake hands once. Three people shake hands three times.
i) How many times would 5 people shake hands
ii) Try and find a general formula.

dumbcow · Answer

i) 10 times
1st guy shakes 4 other people's hands
2nd guy shakes remaining 3 peoples hands
3rd guy shakes remaining 2 hands
4th and 5th guys shake hands
4+3+2+1 = 10


ii) general formula
if there are n people
-->f(n) =  (n-1) + (n-2) +...1
this forms an arithmetic sequence
sum = n(n-1)/2

dumbcow · Answer

there is another way too
are you learning permutations and combinations right now ?

anonymous · Answer

no just number patterns

dumbcow · Answer

ok then that answer is sufficient :)

anonymous · Answer

good grief you must be an genius

dumbcow · Answer

no not at all, just have taken a lot of classes...plus i like math

anonymous · Answer

lol thanks