999 of them.
Infinitely many.
45 to 54
3 499
85 to 94
245 to 254
250 and 349
999 of them.
Ten integers can be rounded off to 280. An infinite number of numbers can be rounded off to 280.
Infinitely many.
Infinitely many.
35 to 44
45 to 54
3 499
85 to 94
Depends. When you round off something, it has to be to a value. 250 rounded off to its nearest tens place would be 250, rounded to its nearest hundreds place would be 300.
Nine of them.