Question

To the nearest ten thousand, the population of Vermont was estimated to be about 620,000 in 2008 . What might have been the exact population of Vermont in 2008

Answer 1

Given the information you presented it is not possible to tell the exact population.
I can say that the least number that rounds up to 620,000 when rounding to the nearest ten thousand is 615,000.  The highest number that rounds down to 620,000 when rounding to the nearest 10,000 is 624,999.  So your exact answer has to be somewhere between 615,000 and 624,999.  
If you left out the multiple choice answers look for a number between the ones I listed above.