Math with Mr. J: Three-Digit Multiplication Review

Introduction

• Purpose: Quick review of three-digit multiplication.
• Audience: High school, college, adult learners, or anyone needing a refresher.

Example 1: Multiplying 325 by 281

1. Set Up: Write numbers vertically

   • 325
   • x 281

2. Multiplication Process:

   • Ones Digit: Multiply by 1 (from 281)

     • 1 x 5 = 5
     • 1 x 2 = 2
     • 1 x 3 = 3

   • Tens Digit: Multiply by 8 (value is 80)

     • Add a zero placeholder.
     • 8 x 5 = 40 (write 0, carry 4)
     • 8 x 2 = 16 + 4 = 20 (write 0, carry 2)
     • 8 x 3 = 24 + 2 = 26

   • Hundreds Digit: Multiply by 2 (value is 200)

     • Add two zero placeholders.
     • 2 x 5 = 10 (write 0, carry 1)
     • 2 x 2 = 4 + 1 = 5
     • 2 x 3 = 6

3. Addition:

   • Add partial products:
     • 325
     • 26,000
     • 65,000
   • Result: 91,325

4. Partial Products Explanation:

   • 325: From 1 x 325
   • 26,000: From 80 x 325
   • 65,000: From 200 x 325

Example 2: Multiplying 6724 by 549

1. Set Up: Write numbers vertically

   • 6724
   • x 549

2. Multiplication Process:

   • Ones Digit: Multiply by 9

     • 9 x 4 = 36 (write 6, carry 3)
     • 9 x 2 = 18 + 3 = 21 (write 1, carry 2)
     • 9 x 7 = 63 + 2 = 65 (write 5, carry 6)
     • 9 x 6 = 54 + 6 = 60

   • Tens Digit: Multiply by 4 (value is 40)

     • Add a zero placeholder.
     • 4 x 4 = 16 (write 6, carry 1)
     • 4 x 2 = 8 + 1 = 9
     • 4 x 7 = 28 (write 8, carry 2)
     • 4 x 6 = 24 + 2 = 26

   • Hundreds Digit: Multiply by 5 (value is 500)

     • Add two zero placeholders.
     • 5 x 4 = 20 (write 0, carry 2)
     • 5 x 2 = 10 + 2 = 12 (write 2, carry 1)
     • 5 x 7 = 35 + 1 = 36 (write 6, carry 3)
     • 5 x 6 = 30 + 3 = 33

3. Addition:

   • Add partial products:
     • 60,516
     • 268,960
     • 3,362,000
   • Result: 3,691,476

Conclusion

• Reviewed multiplication of three-digit numbers using a step-by-step approach.
• Emphasized importance of lining up numbers vertically and using partial products.
• Encouragement for further practice and understanding.