Speaking of nines...

Basic bookkeeping trick: If you add two columns of numbers twice (as you're supposed to do for accuracy) and you come out with differing totals, subtract the lower total from the higher. If the result is nine or any numbers which equal nine when added together, you probably have a transposition problem. For example, if you were supposed to enter "495" and entered "945" the difference in your totals would be 450 and 4+5+0=9. If you were supposed to enter "25" and entered "52" the difference would be 27 and 2+7=9. If the difference doesn't total to nine, you probably fat-fingered a calculator key.