Time

 Rounding is finding the nearest ten, hundred, thousand.

Addition and division are both strategies the are used for rounding. To round the person needs to find the mean, to find the mean get a set of numbers like 5,7,1,9,3 and then add them altogether which would make the number 25. Then divide them by the amount of numbers there are which makes 5.

Now this is were the rounding begins, if the number is 5-9 that makes the number go up. If the number 0-4 it makes the number go down. For example 21.85 then it becomes 21.9