To approximate 25.2871 to the nearest thousandth, we look at the digit in the thousandths place, which is 7 (in 25.2871, the thousandths digit is the third digit to the right of the decimal point).
Next, we check the digit to the right of the thousandths place, which is 1. Since 1 is less than 5, we do not round up.
Thus, 25.2871 rounded to the nearest thousandth is 25.287.