If the amount doubles every two hours, what is the amount after the first two hours?
Then what is the amount after the second two hours?
as this reply suggests, just multiply 200 by 2, twice. since it doubles every 2 hours. thus, it will quadruple after 4 hours. so while the approach of using $\displaystyle P = P_0e^{rt}$ will work, it is overkill
Last edited by mr fantastic; Feb 9th 2009 at 07:14 PM.