Official site with more information and practice: www.mathallstar.org.Remainder does not seem to be a big topic in school math. However, in competition math, it is. Almost every contest at middle school and high school level has remainder related problems. For example, in 2017 AMC 10B, out of total 25 problems, at least 3 are related to this topic: the 14th, 23rd, and 25th.Modular arithmetic is a branch in mathematics which studies remainders and...