Represent collections as equal groups and rectangular arrays, distinguishing the number of groups from the group size and connecting them to skip-counting, repeated addition, multiplication equations, and decomposed arrays, including groups of 2, 5, and 10 within 100. Form and partition exact equal groups or shares, solve for the total, group size, or number of groups using multiplication and division relationships, and recognize odd and even pairings. Solve equal-group and equal-sharing situations with objects, drawings, arrays, bar models, and equations, including missing-factor problems and grouping division within 100, without fractions, remainders, or formal division algorithms.