You can make your life a lot easier by simplifying a lot of the numbers you get. If you see a 8.5, round it up to 10. Make that 426 500. Usually the answers are really far apart (ie - it's 1, 10, or 100), so you just need to figure out what range your answer is in.
If you start multiplying every single number to the 2nd decimal place, you will run out of time. Round, round, round, round, round! 😀
Just doing a bunch of practice MCATs will get you used to the idea of doing math like that in your head or on scrap paper. I think a calculator would help, but you can do it without one without a lot of difficulty...
Just my 2 cents.... 😀