1. Arrays and an expanded algorithm
Lesson 8-2
CCSS 4.NBT.5

2. Warm up Compare these numbers using <, > and =. 4,576 ___ 4,675
254,688 ___ 254,686
133,405 ___ 133,405
790,172 ___ 790,127

3. MATH Essential Questions
How can greater products be found mentally?
MATH
Essential
Questions

4. MATH Essential Questions
How can greater products be estimated?
MATH
Essential
Questions

5. Think and write
How do arrays help you to multiply 2 digit numbers? Do you like using this strategy? Explain.

6. Today’s Lesson
In this lesson, you will use an algorithm to record the partial products as you multiply.
Let’s look at the Envision Video for this lesson and take the quiz.

7. Arrays and Expanded algorithms
During the last lesson, you learned how to make arrays to multiply 2 digit by 2 digit numbers. You break the numbers into tens and ones and outline and shade those areas of the array.
For practice: Make an array to model 12 x 15.

8. using the partial products method16
X 15 30 50 60
+100
240
Step 1: Draw the array for 16 x 15.
Step 2: Start with the ones. (5 x 6 = 30)
Step 3: 5 x 10 = 50.
Step 4: 10 x 6 = 60.
Step 5: 10 x 10 = 100.
Step 6: Add all the partial products.
The answer is 240.

9. Practice!
Use the expanded algorithm and/or draw an array to solve.
18 X 19
23 X 14
21 X 15
24 X 18

10. Problem 1
Mr. Tate plants 17 tomato plants. If each plant has 25 tomatoes on it, how many tomatoes will Mr. Tate harvest? Solve this problem

11. Problem 2
Sharon harvests 18 pumpkins. If each pumpkin weighs 12 pounds, how much will their combined weight be?

12. Problem 3
A batch of Mrs. Moreno’s salsa calls for 14 hot peppers. If she makes 16 batches, how many peppers will Mrs. Moreno use?

13. Problem 4
Ellen harvests 22 zucchinis from her garden to make zucchini bread for her friends. If she slices each zucchini into 17 slices, how many slices will she have in all?

14. Problem 5
There are 16 pea plants in a garden. If each plant is about 19 inches tall, what is the combined height of all of the plants?

15. Lesson Wrap Up
In this lesson, you learned to use the expanded multiplication algorithm to find the product of two 2-digit numbers.
Reflection in Notebook: One thing I learned today was…
Center Activity – (8-2).
Homework (8-2 Practice) for one “Paw Signature” and (8- 2 Reaching & Practice) if you want two “Paw Signatures.”
Website for Practice: Website for Practice: