You want to find the closest ten thousand that there is to 639,121.
So a ten thousand is basically anything that ends with four or more zeros.
For example:
530000 would be a ten thousand because it has four zeros at the end.
So you can see what the closest ten thousands are to 639,121 would be.
They would be:
630,000 and 640,000
Since they both have four zeros at the end.
Now you can just tell that 639,121 is closer to 640,000 because the digit in the thousands place, 9, is closer to 10 than 0.
Hope this helped :)
