B25 — Multiplication within 100: Automatizing the Basic Facts Using the Array

Several pairs of expressions in the two prior strings introduce the commutative property of multiplication. Turn the array to help students see why factors can be commuted—what was a column is now a row. Other pairs are designed to bring up a conversation on what should be removed. For example, in B25, if one commutes the last problem to 8x7, it is easier to see its relationship to 9x7—a row of 7 needs to be removed.