1000
One thousand of them - to the nearest thousand, Two thousand of them - to the nearest two thousand, Four thousnad - to the nearest four thousand None - to the nearest whole number.
1000
0
6500 to 749 9999 of them.
We're rounding to the thousands place. How many thousands are in 3,100? Label the lower endpoint.
21079000000 rounded to the nearest hundred thousand is 21079000000
All numbers can be rounded to the nearest ten.
An infinite number.
530
88500
Infinitely many. There are infinitely many numbers between any two numbers, and infinitely many between any two of those and so on.
There are infinitely many such numbers.