When rounding off, the rule is, "If the first figure to be discarded is 5 or more then the previous figure is increased by 1.
Following this rule then 650 is the result of rounding off numbers in the range 645 to 654.
As 650 itself is not rounded off then there are 9 whole numbers that can be rounded to 650.
700
650
600
To the nearest 100, any number greater than or equal to 650 and less than 750 will round to 700. examples (whole numbers): 650, 651, 749, examples (decimals): 650.5, 749.5, 749.9, 749.999
650
650
650
650
39.665 (rounded)
640
650
650