Explanation:
A tenth is 0.1
To round of to the nearest tenth means to round it of to 1 decimal place.
Now, look at the number after the tenth place with is 0.03 or simply 3.
If the digit is 0-4, you round the whole number down.
Hence, 15.839 is 15.8 to the nearest tenth digit.
If the tenth digit is 5-9 such as 15.85 or 15.87, you round the number up, to give 15.9