Description : Brain Teaser - How does this work?
Last Answer : Starting with n numbers a(1), a(2), ..., a(n) we will always end up with (a(1)+1) ( a(2)+1)...(a(n)+1) -1. The reason is that ab+a+b = (a+1)(b+1) - 1 One way to prove the above ... .(a(n)+1) -1 Calculating (a+1)(b+1)-1 proves the statement for n, which shows the statement is true by induction on n.