Two activities build conceptual understanding of number patterns. First, as kids find common multiples on 10 x 10 charts. Second, they use the Sieve of Eratosthenes to separate prime and composite numbers to 100. Open the preview to take a closer look. 1. Students mark multiples of two through nine on a table. As they work, anew awareness of the base ten system emerges. Kids connect skip counting from earlier grades with multiplication facts. They realize that certain numbers are multiples of m