650. It is already a ten...
650 itself.
See my answer for 1.7. The same thing applies. Tenths is ten. If you want six hundred and fifty, ask about six hundred and fiftyiths.
It already is. 650
660
700
600
64
645
650
650
650
650
640
650
To the nearest ten, 650 To the nearest hundred, 600 To the nearest tenth, 649.0
645 rounded to the nearest ten would simply be 650.
650
650
660
650