To round 173.9 to the nearest tenth, follow these steps:
Identify the tenth place: In the number 173.9, the tenth place is the first digit after the decimal point, which is 9.
Look at the hundredth place: The digit in the hundredth place (the second digit after the decimal point) is 0.
Apply rounding rules: Since the digit in the hundredth place (0) is less than 5, you do not change the tenth place.
Final rounded result: The tenth place (9) remain the same 9, so the number rounds to 173.9.
Thus, 173.9 rounded to the nearest tenth is 173.9.