Since the fourth place is 5 or more (it's 9), the third place is increased by 1. The result is 3.813 .
3.8129 rounded to 3 decimal places is: 3.813
When rounding 3.8129 to three decimal places, you look at the fourth decimal place, which is 9. Since 9 is greater than 5, you round the third decimal place (2) up by 1. The answer, therefore, is 3.813.
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