517.23 was divided by a power of ten to get 5.1723. what power of ten was it divided by?
10
100
1,000

You can see that the point has went 2 numbers backward. Which means that the power of ten that 517.23 was divided by should have 2 zeroes, which is of course 100.
The number of numbers which the point go backward is equal to the number of zeroes contained in the power of 10.
divided by 10, the point go 1 number backward; divided by 10 000 000, the point go 7 numbers backward, etc...

Hope this Helps! :)

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