Gee
So take 2,560,000. Move the period over to a number that's more or equal to 1, but less than 10.
2.560,000 is our new number.
How many spaces did we move to get there?
Counted, it's 6.
So, the answer is 2.56 (get rid of the zeros) x 10^6.
To check your answer, grab your computer calculator and punch the answer in.
It should come up as 2,560,000.
Hope it's helpful 
