It is 2000.
Most schools wrongly teach you to always round 5 (in this case, 50) up so the answer would be 2100 but, while this is a simple rule to teach, it is not really correct. Under this rule:
• if the following digit is 0 you don't round;
• if the following digit is 1, 2, 3 or 4 you round down; and
• if the following digit is 5, 6, 7, 8 or 9 you round up.
As a result you are more likely to round up than round down and that introduces an upward bias into your calculations.
The IEEE (Institute of Electronic and Electrical Engineers) standard 754 is to round 5 up or down so that the new last digit is even. See link for more: //en.wikipedia.org/wiki/Rounding#Round_half_to_even
2000
2050
853 rounded to the nearest 100: 900. 10853 rounded to the nearest 100: 10900.
100
100
0
555 rounded to the nearest 100 is 600.
97 rounded to the nearest hundred is 100. 97 rounded to the nearest ten is 100
100
100
100
0