3.2@#6

IF @ and # each represent single digits in the decimal above,what digit does @ represent??
1. when the decimal is rounded to the nearest tenth,3.2 is the result.
2. when the decimal is rounded to the nearest hundreth,3.24 is the result.

I got the answer as correct(e) but the whole concept of rounding is a bit shaky.Could somebody please treat this question as the "lesson for rounding" or "indepth analysis into decimals" or whatever and explain the A-Z of the concept??

thanks!!