Math Lesson with Mr. J: Multiplying Two-Digit Numbers

Introduction

• The goal of the lesson is to understand how to multiply two-digit numbers by two-digit numbers.
• Two examples are provided to demonstrate the process.
• Key Concept: Product refers to the answer to a multiplication problem.

Example 1: Multiply 39 by 24

1. Setup
   • Write the numbers in a column ensuring digits are aligned by place value.
     • 9 and 4 in the ones place, 3 and 2 in the tens place.
2. Process
   • Step 1: Multiply 4 by each digit in 39:
     • 4 x 9 = 36 (write 6, carry 3)
     • 4 x 3 = 12, plus 3 = 15 (write 5, carry 1)
   • Step 2: Multiply 20 (as 2 represents 20) by each digit in 39:
     • Insert a 0 to shift due to the place value.
     • 2 x 9 = 18 (write 8, carry 1)
     • 2 x 3 = 6, plus 1 = 7
   • Partial Products:
     • 4 x 39 = 156
     • 20 x 39 = 780
3. Combine Partial Products to find the final product:
   • Add 156 and 780:
     • 6 + 0 = 6
     • 5 + 8 = 13 (write 3, carry 1)
     • 1 + 1 + 7 = 9
   • Final Product: 936

Example 2: Multiply 68 by 57

1. Setup

   • Align 68 and 57 properly.

2. Process

   • Step 1: Multiply 7 by each digit in 68:
     • 7 x 8 = 56 (write 6, carry 5)
     • 7 x 6 = 42, plus 5 = 47
   • Step 2: Multiply 50 (as 5 represents 50) by each digit in 68:
     • Insert a 0 to shift due to the place value.
     • 5 x 8 = 40 (write 0, carry 4)
     • 5 x 6 = 30, plus 4 = 34
   • Partial Products:
     • 7 x 68 = 476
     • 50 x 68 = 3400

3. Combine Partial Products to find the final product:

   • Add 476 and 3400:
     • 6 + 0 = 6
     • 7 + 0 = 7
     • 4 + 4 = 8
     • 3 (no carry needed)
   • Final Product: 3876

Conclusion

• Demonstrated the method of multiplying two-digit numbers through aligning digits and breaking down the process into manageable steps.
• Emphasized the importance of understanding place values and carrying numbers correctly.