B2 — Multiplication within 100: Automatizing Basic Facts using the Open Number Line

Note how the first problem of the string will likely be easy for the children? They will either already know this multiplication fact or will be able to quickly generate 4 + 4. The string encourages children to use the first problem to solve the second problem either by thinking about 8 + 8 or by thinking of 2 groups of 2 x 4. If the latter strategy does not come up, wonder aloud if the first problem could be used to solve the second problem. This will support students in using previous problems to solve new problems as the string progresses. [Note: For 10 x 4, if a student says "I added a zero," have a discussion with the class to help them realize that they are not "adding a zero" (as the sum of 4 + 0 is 4, not 40). The problem calls for 10 groups of 4, or 4 groups of ten (the commutative property), which explains why the 4 moves to the left and a zero takes its place.]