Lesson plan

Multiplication: Solving for Unknown Factors

What's the unknown? In this lesson, your students will become familiar with strategies that can help them solve for the unknown factor in multiplication problems.
GradeSubjectView aligned standards

Students will be able to solve for the unknown factor in multiplication problems.

(10 minutes)
  • Tell your students that today they are going to learn strategies for solving for the unknown factor involving multiplication problems.
  • Ask your students to share division strategies they know.
  • As the students share, list the strategies on the board. Your students might offer suggestions such as repeated subtraction or arrays.
(15 minutes)
  • Write a few multiplication problems on the board with an unknown factor. For example, 6 x ____ = 36.
  • Have your students rewrite the problem as a division problem, as follows: 36 ÷ 6 = _____.
  • Ask your students to choose an effective division strategy that they know.
  • Solve the problem using repeated subtraction: 36-6=30-6=24-6=18-6=12-6=6-6=0.
  • Then, show your students how to solve the problem using arrays or grouping: XXXXXX XXXXXX XXXXXX XXXXXX XXXXXX XXXXXX
  • Explain to your students how you got the answer 6.
(15 minutes)
  • Have your students solve _____ X 5 = 40Using what they think is the most efficient strategy.
  • Ask for volunteers to raise their hands and share with the class the steps to solve the problem.
  • As the problem is being solved aloud, write down the steps on the whiteboard.
  • When the problem is done, review it with the class for accuracy.
(15 minutes)
  • Give the students the Solve the Unknown Factor worksheet to complete.
  • Enrichment:Have your students skip the division step on their papers to solve the multiplication problems. Encourage them to memorize multiplication facts to quickly solve problems.
  • Support:Give your students simpler problems to solve, such as 3 x ___ = 12. Use manipulatives to help show grouping and arrays.
(10 minutes)
  • Walk around and observe the students as they work on completing the assignment.
  • Monitor the students as they work, making sure that the problems are done correctly.
(10 minutes)
  • Ask for volunteers to share their answers and justification.
  • As the problems are reviewed in front of the class, have the students check their answers for accuracy.

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