MathCastle
Groups and FieldsMediumSubgroups and Cyclic Groups

Subgroups and Cyclic Groups · Medium problem

How many of these subsets of (Z12,+)(\mathbb Z_{12},+) are subgroups? {0,6}\{0,6\}, {0,3,6,9}\{0,3,6,9\}, {0,4,8}\{0,4,8\}, {0,2,4}\{0,2,4\}, {0,5,7}\{0,5,7\}.