Review Multiplication Strategies. All students should have completed Question 14 and Check-In: Question 23 of the Workshop: Multiplication Strategies pages in the Student Guide. Discuss solution strategies to each of the questions including the steps students took in solving the multistep problems.
Ask questions such as the following:
- Did you need to estimate or calculate exactly?
- Show us the method you used to multiply.
- Why did you use that method?
- Do all the strategies make sense for every problem?
(Possible response: No. For example, using rectangles is not a very efficient way to solve most problems, but it does help me understand multiplication using partial products. I like to use the compact method when the problem involves multiplication of a multidigit number by a single-digit number, like 345 × 6. But when it is two-digit by two-digit, it is clearer and easier for me to use all-partials and then I make less mistakes.)
- Did anyone use a mental math strategy? Explain.
- How can you tell if your answer is reasonable?
(Use another strategy to check, use mental math,
or use an estimation strategy.)
- How did you label your answer?
Play Multiplication Digits Game. Conclude the lesson by providing time for students to play the Multiplication Digits Game. Students will apply place value concepts and mathematical properties involved in multidigit multiplication, and practice the estimation and multiplication strategies they have worked on throughout the Workshop.
Arrange students in small groups to play. Student groups will need a set of 0–9 Digit Cards, paper, and pencils. Ask students to use the templates shown in Figure 6. See Meeting Individual Needs, which includes Figures 7 and 8, for ways to differentiate the games.
For students who need extended practice with multiplication strategies, make the following adjustments to the game:
- Change the rules of the Multiplication Digits Game so that players only fill in the boxes after all the cards have been drawn and displayed.
- Focus the activity on practicing various strategies for multidigit multiplication. Ask students to try different strategies from the Multidigit Multiplication Strategies Menu until they find one with which they feel comfortable.
- Ask students to discuss strategies for winning the game in terms of partial products and place value. For example, ask:
- Where should you put the largest digits to get the largest product? (in the position of highest place value for either factor)
- Why does putting a large digit there make the product larger? (The large digit takes on the place value of the highest-value place, or else it gets multiplied by the highest place-value digit of the other number, resulting in the largest partial product.)
- For students who are having particular difficulties using the multiplication strategies, ask them to use the templates in Figure 7 that involve multiplication of two- and three-digit numbers by one-digit numbers.
For students who are able to use methods flexibly to multiply the numbers in these templates, extend learning by introducing the following variations:
- Use the templates in Figure 8 to introduce multiplication with larger numbers.
- Change the rules of the game so that the smallest product wins instead of the largest product.
