It's 510,000. Just go to the 10,000 place and round there, then just replace the rest of the numbers with 0's. Don't use a decimal; that would suggest that the number isn't rounded.
510000 is the correct answer. you go to the 10000 place and look at the digit to the left. of the number is 5 or higher, the 10000 place will increase by one and ey other number to the left changes to zero. If lower than 5, then the 10000 place stays the same and every other number to the left changes to a zero.
