Display and ask students to study the Multidigit Multiplication Strategies Menu in the Student Guide Reference section. See Figure 8. Discuss the different strategies with the students.
- Do you recognize the strategies we have been discussing?
- Which is your favorite strategy to use? Why?
- Do some strategies work better for some kinds of problems?
- Can you give an example of a problem for which a mental math strategy would be most efficient? (Possible response: using simpler numbers, e.g., 18 × 6 = (20 × 6) − (2 × 6))
- Can you give an example of a problem for which a paper-and-pencil method would be most efficient and show how to do it? (Possible response:
The Multidigit Multiplication Strategies Menu was developed and generalized in earlier grades. The menu is a summary of the types of mental math, paper-and-pencil, and estimation strategies students might use. Students should be encouraged to use whatever strategy makes sense to them and seems to make sense for the problem. Encourage students to add their own invented strategies to the menu using self-adhesive notes. Also encourage students to use strategies that they are not familiar with.
Use Check-In: Questions 17–19 in the Student Guide with the corresponding Feedback Box in the Teacher Guide to assess students' abilities to multiply multidigit numbers using mental math and paper-and-pencil methods (expanded form, rectangle mode, all-partials, compact) [E4]; choose appropriately from among mental math, estimation, and paper-and-pencil methods to find sums, differences, and products [E6]; choose a strategy for solving the problem [MPE2]; and check calculations [MPE4].
For students ready for a challenge, have them write their own multiplication problems. These problems can be swapped with other students and solved.
For students having difficulty keeping digits in the correct place value position when using the all-partials method, have students write their problems on centimeter grid paper with one digit in a box.
