It is 999, exactly as in the question.
1,000
245 to the nearest hundred is 200.
409 to the nearest hundred is 400
3486 rounded off to the nearest hundred is 3500.
548.48 rounded off the nearest hundred is 540.
593 656 rounded off to the nearest hundred is 593 700.
833 rounded off the nearest hundred is 800.
600
409,381,900
10100
3600