100
It is 999, exactly as in the question.
1,000
To round off 78 to the nearest hundred, you look at the tens digit, which is 7. Since 7 is greater than 5, you round up. Thus, 78 rounded to the nearest hundred is 100.
900
2,600
It is 999, exactly as in the question.
1,000
409 to the nearest hundred is 400
548.48 rounded off the nearest hundred is 540.
3486 rounded off to the nearest hundred is 3500.
593 656 rounded off to the nearest hundred is 593 700.
833 rounded off the nearest hundred is 800.
409,381,900
10100
900
3600
2,600