To round 39918.23 to the nearest thousandth, follow these steps:
Identify the thousandth place: In the number 39918.23, the thousandth place is the third digit after the decimal point, which is 0.
Look at the ten-thousandth place: The digit in the ten-thousandth place (the fourth digit after the decimal point) is 0.
Apply rounding rules: Since the digit in the ten-thousandth place (0) is less than 5, you do not change the thousandth place.
Final rounded result: The thousandth place (0) remain same 3, so the number rounds to 39918.23
Thus, 39918.23 rounded to the nearest thousandth is 39918.23