Decimal numbers can be rounded off to the number of decimal places that we need.
To round off 6.2197 to one decimal place,
Look at the digit in the second place. (1)
Round down if 0,1,2,3 or 4.
This means, write the original number in the first decimal place, leaving off all other digits that come after. (2)
The answer is 6.2
To round off 3.789 to two decimal places,
Look at the digit in the third place. (9)
Round up if 5,6,7,8 or 9.
This means write the original number plus one in the second decimal place, leaving further digits. (8+1=9)
The answer is 3.79