Is the remainder of a negative number divided by a positive number negative?

Answer 1

A subtle point is that the remainder is always a positive number. So -7 divided by 3 is -3, remainder 2 (rather than -2, remainder -1). This is important for the date of Easter because we must often calculate the remainder when dividing into a negative number. Since in that case we are not interested in the quotient it is sufficient to calculate the negative remainder and then simply add to it the number we were dividing by. So -11 mod 3 may be calculated as: -11 divided by 3 is -3, remainder -2, so the number required is -2 + 3 = 1.