Infinitely many numbers.
101 whole numbers . Although, technically 800, itself, would not be rounded. This would comprise the numbers from [750, 850]. In the first case the 5 is rounded up while in the second it is rounded down. This is consistent with the rule of "Round up or down so that the new last digit is even". This is the default rounding mode used in IEEE 754 computing functions and operators.
All numbers can be rounded to the nearest ten.
There are infinitely many such numbers.
999 of them.
70
0
All numbers can be rounded to the nearest ten.
An infinite number.
530
88500
The numbers 250-259 can be rounded to 300. Also 301-349 can be rounded down to 300. This works if you are rounding by the nearest hundreds place.
1000
There are infinitely many such numbers.
999 of them.
Well, isn't that a happy little question! When you round numbers to the nearest 500, you can round any number to the nearest 500. That means there are infinite numbers that can be rounded to 500. Just remember, there are no mistakes in rounding, only happy little accidents!
70
70
33,500,000 to 34,499,999