Math module 3 lesson 20
- 1. Multiplication of Single-Digit Factors and Multiples of 10 Module 3: Lesson 20 Objective: Use place value strategies and the associative property n × (m × 10) = (n × m) × 10 (where n and m are less than 10) to multiply multiples of 10.
- 2. Group Counting (3 minutes) Sixes to 60 Sevens to 70 Eights to 80 Nines to 90
- 3. Multiply by Different Units (6 minutes) 2 × 3 = ____ Say the multiplication equation in unit form. Say it in standard form. 2 tens × 3 = ____ On your boards, write the multiplication equation. Below your equation, write a second multiplication equation in standard form. Continue with the following possible sequence: 4 × 2, 4 tens × 2, 5 × 3, 5 × 3 tens, 6 × 4, 6 × 4 tens.
- 4. Multiply by Different Units (6 minutes) Write 7 × 6 = ____ Say the multiplication equation. Write 70 × 6 = ____ Write the multiplication equation. Continue with the following possible sequence: 8 × 8, 8 × 80; 9 × 8, 90 × 8; 6 × 6, 60 × 6; 8 × 7, 8 × 70; 4 × 9, 40 × 9; 9 × 6, 90 × 6.
- 5. Write In the Parentheses (6 minutes) 4 × 5 = 2 × 2 × 5 What’s 4 × 5? On your boards, copy the equation. Then write in parentheses and solve. Continue with the following possible sequence: 6 × 4 = 6 × 2 × 2, 6 × 6 = 6 × 2 × 3, 4 × 7 = 2 × 2 × 7, 7 × 8 = 7 × 4 × 2, 8 × 4 = 8 × 2 × 2, 8 × 6 = 8 × 3 × 2, 9 × 6 = 9 × 3 × 2, 9 × 8 = 9 × 4 × 2.
- 6. Application Problem (5 minutes) Model 3 × 4 on a place value chart. Then explain how the array can help you solve 30 × 4.
- 7. Application Problem (5 minutes) Model 3 × 4 on a place value chart. Then explain how the array can help you solve 30 × 4.
- 8. Concept Development (30 minutes) 40 × 2 Which tens fact gives us a product of 40? (10 × 4) × 2 Why do you think I put 10 × 4 in parentheses? Let’s move the parentheses to change the way the numbers are grouped. On your board, use the parentheses to group the numbers differently. Is this problem friendlier than 40 × 2? Repeat the process with 20 × 3, 30 × 3, and 50 × 2.
- 9. Concept Development (30 minutes) Use the chart to write a multiplication equation in unit form. Now I want to multiply my 18 ones by ten. Watch as I show this on the chart. I redraw my dots into the tens place and draw an arrow (draw arrow) to remind myself that they move to the next unit. Let’s multiply our 3 groups of 6 ones by 10. (3 × 6 ones) × 10 = _____ What is the answer to 18 ones × 10 in unit form? What is the value of 18 tens?
- 10. Concept Development (30 minutes) This time I already moved my 6 ones to make them 6 tens. Use the chart to write a multiplication equation in unit form. Now I want to multiply my 6 tens by 3. How many rows do I need to add to show 3 rows of 6 tens? (Add 2 rows of 6 tens and write 3 × (6 × 10).) How does my array show this expression? Tell your partner. What is the answer to 3 × 6 tens in unit form? Compare the equations (3 × 6 ones) × 10 and 3 × (6 × 10). What do you notice about the factors we used? Repeat the process with (4 × 5) × 10 and 4 × (5 × 10).
- 11. Problem Set (10 minutes) Student Debrief (10 minutes) Exit Ticket (3 minutes)
- 12. Homework 3-3 Lesson 20 Homework Is Due Tomorrow!