5050 to the nearest 100

It is 5000.

Most schools teach you to always round 5 up (so the answer would be 5100) but while this is a simple rule to teach, it is not appropriate. Under this rule: · if the following digit is 0 you don't round; · if the following digit is 1, 2, 3, 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 be rounding up than rounding down and that introduces an upward bias into the calculation.

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