The richest man of all time, when wealth is measured as a percentage of the national economy, was John D. Rockefeller, whose fortunes made Gates' and Buffet's look downright puny. Keeping score of who's wealthier is like a spectator sport with Forbes magazine as its official referee.
OH NO, I am not allowed a calculator on the MCAT!!! If you reading this you have probably completed all the general requirements to take the MCAT. Thinking back over your semesters of chemistry you would of used your calculator a lot to complete the math problems ranging from the basics of stoichiometry to the complex problems of solving the pH of a weak acid.
Well the TI-84 is great and is what I use. There is no problems with it. However, the TI-89 it the upgrade of it that will work wonders with multi-variable equations and derivatives/integrals. Beware that the TI-89 is not a calculator allowed on the ACT but it fair game for the SAT and AP testing. If you happy with TI-84 then I'd stick with that. I agree if you're working well with the TI-84 there's no need to change. As stated the 89 isn't allowed in the ACT.