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### Lesson plan

# Multiplying by Multiples of 10

#### Learning Objectives

Student will be able to multiply a one-digit number by a multiple of ten.

#### Introduction

*(1 minute)*

- Tell students that today, they will be learning how to multiply any one-digit number by a multiple of ten.
- Ask students to skip count by 10 to 100 together.
- Explain that your class will be focusing on two-digit multiples of ten for this lesson: 10, 20, 30, 40, 50, 60, 70, 80, and 90.

#### Explicit Instruction/Teacher modeling

*(14 minutes)*

- On the board, write a list of sample multiplication problems, including the product. Each problem should have a one-digit number and a two-digit multiple of ten. For example,
**3 x 40 = 120, 5 x 60 = 300, 7 x 70 = 490, 2 x 50 = 100, 80 x 2 = 160, 40 x 4 = 160.** - Ask your students to turn to a neighbor and discuss any patterns they see.
- Request that your students share their thoughts after a few minutes of discussion. Students may report that they see the simple problem inside of the larger problem. Say, "I see
**7 x 7**in**7 x 70**. The answer to**7 x 7**is 49, and the answer to**7 x 70**is 490. So there is an extra zero on both sides of the equal sign." - Tell the class they'll be learning different strategies for solving these types of problems.
- Write another sample problem on the board. For example,
**30 x 6 = ?**. - Explain to your class that the first strategy they can use to solve this problem is the
*sketch strategy*. Draw straight lines to represent base-ten sticks, and include the correct number of "groups" (represented by the one-digit number in the problem) in your drawing. For example:*Draw a picture of 6 groups of 30.*`III III III III III III`

- To solve, model counting each base-ten stick (by tens) for an answer of 180.
- Keeping the same problem on the board, model a second strategy of
*underlining*by drawing a line under the one-digit number, and the number in the tens place of your two-digit number. In this example, you'll underline the numbers 3 and 6. This will reveal the basic math problem*3 x 6*. - Write your new basic equation on the board, including the product. In this case:
*3 x 6= 18*. - Explain to your class that the 18 represents the number of tens, or
*18 x 10 = 180*.

#### Guided Practice

*(10 minutes)*

- Pass out a dry erase board and marker to each student.
- Instruct your students to write a multiplication problem on their dry erase board, such as
**7 x 30**. - Tell students that you would like them to solve this problem using the sketch strategy.
- Guide students to draw seven groups of 30 on their boards. It should look like this:
`III III III III III III III`

- Ask your students to count their base-ten sticks by tens to solve the equation. Your students should come up with 210 as the product.
- Instruct your students to solve the same problem using the second strategy. They must show their work on their individual dry erase boards.
- Tell your students to find the simple multiplication problem and write it on their board. For example:
**7 x 3**. Tell them to solve the simple multiplication problem. They should get a product of 21. - Choose a volunteer to tell you what 21 tens is, or
**21 x 10**. You should receive the answer 210. - Monitor your students' understanding of these concepts. If students are doing well, move onto the next activity. If not, repeat these steps with one or two more problems.

#### Independent working time

*(15 minutes)*

- Instruct your class to find a partner for the next activity.
- Pass out Multiplying Madness Game Sheet and 10-sided die to each pair of students.
- Read the directions on the game sheet with the class, and answer any questions your students may have.
- Once you've answered any questions, instruct your students to begin playing.
- Circulate while your students are playing the game to answer any questions.

#### Differentiation

**Enrichment:**

- Challenge advanced students to write 3 word problems using multiples of ten on the back of their worksheets.

**Support:**

- Work with a group of struggling students on the first three problems on the Silly Seahorse Multiplication Practice worksheet. Model and work step-by-step as a group to monitor understanding. Give students who are having trouble a multiplication table to work with.

#### Assessment

*(14 minutes)*

- Pass out a copy of the Silly Seahorse Multiplication Practice worksheet to each student.
- Students will work independently to complete the worksheet.
- As students complete the worksheet, check for understanding and reteach individuals as necessary.

#### Review and closing

*(1 minute)*

- Ask the students which strategy they liked using better today, making a sketch or solving the basic fact and the multiplying by ten. Encourage your class to talk with their partners about why they liked using that strategy best.
- Remind your students that either strategy will work for this type of problem when used correctly and as mathematicians, they can decide which strategy works best for them.