999 of them.
Infinitely many.
3499
45 to 54
85 to 94
Since numbers equal to or greater than 5 are rounded up, and numbers equal to or less than 4 are rounded down, the largest 4-digit number that can be rounded off to 3000 would be 3004.
2645 rounded to the nearest thousand is 3000.
3000
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.
3499
35 to 44
245 to 254
45 to 54
The largest 4 digit number that can be rounded off to 3000 is 3499. If 3499 is rounded to nearest thousand then we get 3000 but if we consider a number greater than 3499 then rounding off yields 4000. So, 3499 is the required number.