845 rounded to the nearest hundred is 800. This is because the value in the tens place "4" is less than 5.
500
900
7000
800
300
2400
To the nearest hundred it is zero and to the nearest hundredth, which you may have meant, the value will not change at all.
To the nearest hundred, 100.
25000
To the nearest hundred million
845 rounded to the nearest hundred is 800. This is because the value in the tens place "4" is less than 5.
500
100.00
5,451 rounded to the nearest hundred is: 5,500. This is because the value in the tens place is "5". When rounding anything equal to or greater than 5 gets rounded up while everything else gets rounded down.
900
1,565 to the nearest hundred is: 1600. This is because the value in the tens place "6" is equal to or greater than 5. Anything below 5 would need to be rounded down.