Ten of them.
430
16000
98600
Ten integers can be rounded off to 280. An infinite number of numbers can be rounded off to 280.
Ten of them.
999 of them.
999 of them.
2545 to 2554
20000 times
Nine of them.
99 of them.
6500 to 7499 -- 1000 numbers
0
Ten whole numbers can be rounded to 30. The numbers are 25, 26, 27, 28, 29, 30, 31, 32, 33 and 34. There are an infinite number of complex numbers in the interval [25,35) that can be rounded to 30.
3 and these are 600,650,and 700
There are 304.8 millimetres in one foot. Therefore, rounded to two decimal places, 20000 millimetres is equal to 20000/304.8 = 65.62 feet.