SOLUTION: there's a total of 78 handshakes and the equation is h=p(p-1)/2 so how many people are there in a group?

Algebra ->  Customizable Word Problem Solvers  -> Evaluation -> SOLUTION: there's a total of 78 handshakes and the equation is h=p(p-1)/2 so how many people are there in a group?      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 451003: there's a total of 78 handshakes and the equation is h=p(p-1)/2 so how many people are there in a group?
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
h=p(p-1)/2
set h to 78 and solve for p:
78=p(p-1)/2
156=p(p-1)
156=p^2-p
0=p^2-p-156
0=(p+12)(p-13)
p = {-12, 13}
throw out the negative solution leaving
p = 13 people