First find the place that is the thousandth place. That would be the 3 then you will look beside the 3 to see if their is a number bigger than five. If there is then you would add whatever number to make the number 10. In this case their is not so you would instead look at the three and replace all the numbers to the right of three ( don’t change three though) and make them zeros. So that will leave you with 299.2130 rounded to the nearest thousandth.
