618.40
18.64 rounded to the nearest tenth is 18.6
You do not need to do anything. However, in order to SHOW that the number is to the nearest thousandths you may wish to write it as 0.750
170
It is 8.0 : the trailing 0 is necessary to show that it has been rounded to the nearest tenths.
3.810
91.000
402.000
It is rounded to the nearest thousandth so runding to the nearest millionth makes no difference. If you want to show that the number is ACCURATE to the nearest millionth, you could write it as: 4.613000
71956.00
4839.0
221.0
618.40
1.20
267.90
9837.0
2810000 is already rounded to the nearest tenth. If you need to show that it is rounded to the nearest tenth you would need to write it as 2810000.0