1. There will a lot but I am just going to show some of the possible answers:
we are going to use numbers from 1 to 7 and rounded it to 6 300 000.
The given number has 7 digits and numbers from 1 to 7 also have 7 digits
=> 1 2 3 4 5 6 7 (now, arrange to get the correct answer)
=> 6 321 457 , since the number next to 3 is lower than 5, then rounding down will apply
=> 6 300 000
Another example:
=> 6 275 341, since the number next to 2 is higher than 5, which is 7, rounding up will apply
=> 6 300 000