October 11, 2015
by Jennifer Armstrong
Lesson Plan:

Multiplying by Multiples of 10

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

(1 minute)
  • Tell students that today, they will be learning how to multiply any one-digit number by a multiple of ten.
  • 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.
(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. For example: 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 0 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.
  • 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.
(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:
  • 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 class' 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.
(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.
  • 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 seahorses 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.
(14 minutes)
  • Pass out a copy of the Silly Seahorses multiplication 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.
(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.

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