when I use the Sum function to calculate about 10,000 numbers, which have
been rounded to 2 decimals (using the round function in excel), the result of
sum came out with more than 2 decimals. It is eight decimals!
I don't know why, and I split the numbers into several groups. I find that
an interesting thing, the sum of Group A has two decimals, the same with
Group B. But when I calculate the sum of the two groups, the result also came
out with 8 decimals!!!...