Quote from bwolinsky:
All right. I don't know why what I was doing didn't work like that, but they are the same. Done it twice in my calculator in addition to an e-mail.
Case A:
Start with $1000
End of year 1 you have: $1000*1.2 = $1200
End of year 2 you have: $1200*1.2 = $1440
End of year 3 you have: $1440*1.2 = $1728
End of year 4 you have: $1728*1.2 = $2073.6
End of year 5 you have: $2073.6*.5 = $1036.8
Case A:
Start with $1000
End of year 1 you have: $1000*.5 = $500
End of year 2 you have: $500*1.2 = $600
End of year 3 you have: $600*1.2 = $720
End of year 4 you have: $720*1.2 = $864
End of year 5 you have: $864*1.2 = $1036.8
Because you were using the wrong formula.
It is just a future value problem that you execute twice for each case. Once to desribe the 4 20% returns and once to describe the minus 50% return.
FV = PV(1+i)^n