If you round numbers in Excel using the Increase Decimal or Decrease Decimal buttons on the Home tab of the ribbon bar, Excel still does its calculations on the full number. Those two buttons are only formatting, and the full number can rear its head elsewhere on the sheet. If you want to really round numbers, use the ROUND function. Its syntax is:
=ROUND(number to be rounded, number of decimal points)
You can also force a number to be rounded up or rounded down regardless of its natural value using the ROUNDUP and ROUNDDOWN functions, which use the same syntax. And if you place a minus sign before the second argument, Excel will round to the nearest 10 value. Here are some examples, rounding the formula of =97/13:
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