There's a lesson in this... You always need to double check your numbers to verify that you're calculating things correctly. If you plan on pursuing further education in a STEM field, get used to this. The sooner the better. Believe me, I know from personal experience. One thing that would be helpful for you is to get a good understanding of scientific notation and working with several numbers with exponents simultaneously. It can seem daunting at first, but it's nothing more than learning a few small rules, and applying basic arithmetic to the exponents. It's nothing to get flustered over. Also, you could go ahead and write out the long version of whatever it is you're doing... Soon enough you'll understand clearly why scientific notation is even a thing - Dealing with very large numbers is much simpler when you just account for the exponent rather than checking if you've counted the number of zeros correctly. And I won't even get into the debate over whether SI units with prefixes are still SI units.