To summarize the lesson, ask students to use the multiplication patterns to complete the Professor Peabody's Table page in the Student Activity Book. Encourage students to use their multiplication tables to help them. When students are finished, display the page. Discuss strategies for completing the table.
- How did you solve the problems in the 5s row? (Possible response: I filled in the 10s row first because that was easier for me. I know 5 is half of 10 so I divided those numbers in half to fill in the row for the 5s. For example, 10 × 60 = 600 so 5 × 60 = 300.)
- How did you solve the problems in the 9s row? (Possible response: I thought about the patterns chart. When I multiplied 9 × 2, 9 × 3, 9 × 4 and so on, the tens digit went up by 1 and the ones digit went down by 1. The pattern was 18, 27, 36. Because I was multiplying by tens, I added one zero to the end of each product, 180, 270, 360.)
- Look across the row for 4. Do all the products follow the same pattern? Why or why not? (Possible responses: They all have a zero on the end. They all follow the pattern for tens: 4 times 1 ten is 4 tens or 40. 4 times 2 tens is 8 tens or 80. 4 times 3 tens is 12 tens or 120, and so on.)
- Do they all have just one zero on the end? (No. 4 × 50 is 200. That one has 2 zeros.)
- Does 4 times 50 equal 200? Solve it another way to check. (Yes. It is like 4 times 50¢ and that's $2 or 200¢. You can double 50 and get 100 and double again and get 200.)
- Why does it have two zeros? Does it follow the pattern? (Yes. If you multiply the first digits, you get 20. 4 times 5 is 20 and then add one zero to 20 and you get 200. The first zero is from the 20 and then you add another one to follow the pattern.)
- Which problems on Professor Peabody's table were the hardest to solve? How did you solve them?
- If Professor Peabody asked for advice about multiplying by tens or hundreds, what would you tell him? (Answers will vary. Possible responses: It's easy when you follow the pattern. Don't forget you are multiplying tens and hundreds, so your products will end in zeros. Beware of problems that make an "extra" zero like 2 × 50 or 2 × 500.)
Use the Professor Peabody's Table page in the Student Activity Book to assess students' progress toward the following Expectations:
- Use strategies to solve multiplication problems [E2].
- Use turn-around facts to solve multiplication problems [E4].
- Identify and use patterns to solve the multiplication facts for the 2s, 3s, 5s, 10s, 9s, and square numbers [E5].
- Multiply numbers that are multiples of 10 [E7].
The Workshop in Lesson 10 provides targeted practice opportunities for using strategies to solve the multiplication facts.
