What does 7 × 8 mean?

7 × 8 means 7 groups of 8, or 8 + 8 + 8 + 8 + 8 + 8 + 8.

How could you use an array to find the product 7 × 8?

I could draw a rectangle with 7 rows and 8 columns. There are 56 squares. The product is 56.

How does the product 7 × 8 relate to the area of a rectangle?

A rectangle with width 7 units and length 8 units has an area of 56 square units.

How can you multiply 6 × 50 using place value?

There are 6 groups of 5 tens, which is 30 tens. 30 tens is 300. 6 × 50 = 300.

How could you multiply 9 × 35 using an area model?

I could draw a rectangle and divide it into two sections. At the top I write 30 and 5. At the left side I write 9. Then I multiply 9 × 30, which is 270, and multiply 9 × 5, which is 45. Then I add the partial products: 270 + 45 = 315. 9 × 35 = 315.

How do the numbers at the top of an area model relate to place value?

The number 35 is 3 tens and 5 ones. The left box is tens, so I write 30, and the right box is ones, so I write 5.

How would the rectangle change if the problem is 9 × 4,735? How does the change relate to place value?

I would need 2 more boxes, one for the hundreds place and one for the thousands place. Then I would label them 4,000 and 700. Then I can multiply 9 × 4,000, which is 36,000, and 9 × 700, which is 6,300. Then I add all four partial products: 36,000 + 6,300 + 270 + 45 = 42,615. 9 × 4,735 = 42,615.

How could you multiply 26 × 81 using an area model?

I could draw a rectangle and divide it into four sections. At the top I would write 80 and 1 above the two sections. At the top left side I would write 20 and the bottom left side I would write 6. Then I multiply in each section: 20 × 80 = 1,600, 20 × 1= 20, 6 × 80 = 480, and 6 × 1 = 6. Then add the parts: 1,600 + 20 + 480 + 6 = 2,106. So 26 × 81 = 2,106.

Erin says that 57 × 34 = 1,528. Is she correct? Explain.

No. She multiplied 50 × 30 = 1,500 and 7 × 4 = 28. She left out two more partial products: 50 × 4 = 200 and 7 × 30 = 210. The product is 1,938.

Multiplying Up To 4 Digits (Area Model)

LESSON MATERIALS move

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What you will learn from this videoWhat you will learn

How to multiply 4-digit numbers by a one-digit number!
How to multiply two-digits by two-digit numbers!
And, we'll see that multiplying larger numbers can help us pack for camping, study fascinating new animals, and keep track of our favorite collections.

Discussion Questions
- Before Video
  What does 7 × 8 mean? ANSWER
  - 7 × 8 means 7 groups of 8, or 8 + 8 + 8 + 8 + 8 + 8 + 8.
  How could you use friendly numbers to find the product 7 × 8?ANSWER
  - (5 + 2) × 8 = 40 + 16 = 56
  How could you use an array to find the product 7 × 8?ANSWER
  - I could draw a rectangle with 7 rows and 8 columns. There are 56 squares. The product is 56.
  How does the product 7 × 8 relate to the area of a rectangle?ANSWER
  - A rectangle with width 7 units and length 8 units has an area of 56 square units.
  How can you multiply 6 × 50 using place value? ANSWER
  - There are 6 groups of 5 tens, which is 30 tens. 30 tens is 300. 6 × 50 = 300.
- After Video
  How could you multiply 9 × 35 using an area model? ANSWER
  - I could draw a rectangle and divide it into two sections. At the top I write 30 and 5. At the left side I write 9. Then I multiply 9 × 30, which is 270, and multiply 9 × 5, which is 45. Then I add the partial products: 270 + 45 = 315. 9 × 35 = 315.
  How do the numbers at the top of an area model relate to place value?ANSWER
  - The number 35 is 3 tens and 5 ones. The left box is tens, so I write 30, and the right box is ones, so I write 5.
  How would the rectangle change if the problem is 9 × 4,735? How does the change relate to place value?ANSWER
  - I would need 2 more boxes, one for the hundreds place and one for the thousands place. Then I would label them 4,000 and 700. Then I can multiply 9 × 4,000, which is 36,000, and 9 × 700, which is 6,300. Then I add all four partial products: 36,000 + 6,300 + 270 + 45 = 42,615. 9 × 4,735 = 42,615.
  How could you multiply 26 × 81 using an area model?ANSWER
  - I could draw a rectangle and divide it into four sections. At the top I would write 80 and 1 above the two sections. At the top left side I would write 20 and the bottom left side I would write 6. Then I multiply in each section: 20 × 80 = 1,600, 20 × 1= 20, 6 × 80 = 480, and 6 × 1 = 6. Then add the parts: 1,600 + 20 + 480 + 6 = 2,106. So 26 × 81 = 2,106.
  Erin says that 57 × 34 = 1,528. Is she correct? Explain.ANSWER
  - No. She multiplied 50 × 30 = 1,500 and 7 × 4 = 28. She left out two more partial products: 50 × 4 = 200 and 7 × 30 = 210. The product is 1,938.
Vocabulary
- Multiply DEFINE
- Digit DEFINE
- Repeated Addition DEFINE
- Area DEFINE
- Area Model DEFINE
- Rectangle DEFINE
- Place Value DEFINE
- Friendly Number DEFINE
- Vertical DEFINE
- Corresponding DEFINE
- Partial Products DEFINE
- Product DEFINE
- Horizontal DEFINE
Reading Material
Practice Word Problems
Practice Number Problems
Lesson Plan
Teacher Guide
Assessment
Online Quiz Game Quiz PDF Exit Ticket