To round to the nearest tenth you have to look at the hundredth place...in this case 0 is in the hundredth place so you just keep the 9 in the tenth place and drop all trailing numbers...
15.909333 to nearest tenth is:
15.9
You always look at the term after the term you want to round, if that next number is less than 5 you keep term you are rounding to, if it is 5 or greater you round up to the next number.
