# Division: Solving for Unknown Factors

• Math
• 100 minutes
• Standards: 3.OA.A.4
• no ratings yet
September 1, 2015

Help your class conquer division with this lesson that has them find the unknown factor using multiplication!

### Learning Objectives

Students will be able to solve for the unknown factors in division problems.

## Lesson

### Introduction (15 minutes)

• Invite students to bring their math journals and a pencil to the class meeting area.
• Have students place their supplies on the floor next to them.
• Tell students that today they're going to learn strategies for solving division problems.
• Let the students know that to solve for the unknown factor in a division problem, they must have a strong grasp of some multiplication strategies and multiplication facts.
• On the board write “Multiplication Strategies.”
• Then ask the students to share with the class some multiplication strategies they already know. As the students share, list the strategies on the board under the term “Multiplication Strategies.”
• Some strategies students may share are repeated additions, arrays, skip counting, or grouping.

### Explicit Instruction/Teacher Modeling (15 minutes)

• Direct the students’ attention to the board.
• Write a few division problems on the board with an unknown factor. For example: 36÷__= 4; __÷5= 8.
• Tell the students that the first thing we want to do is rewrite the problem as a multiplication problem. For this example: 4x __ = 36 and 5x8 = __.
• Next, tell the students that we need to decide which multiplication strategy to use to solve for the unknown factor. This is an important step as you want the students to choose a strategy they know as well as one that is efficient.
• With student input, solve one of the above problems, using at least three of the strategies referred to above.

### Guided Practice/Interactive Modeling (15 minutes)

• Tell the students to pick up their supplies and write down and solve the other problem using what they think is the most efficient strategy on the board.
• Ask for volunteers to raise their hands and share with the class the steps involved in solving the problem.
• Give the students time to solve the problem.
• As the problem is being solved aloud by the class write down the steps volunteered by the students on the white board.
• When the problem is finished, review it with the class for accuracy. Make sure everyone has the problem written down to use as a reference for completing their assignment during independent work time.

### Independent Working Time (30 minutes)

• Send the students back to their seats.
• Give students the Solve for the Unknown worksheet.
• Walk around and observe the students as they work on completing the assignment.
• Monitor the students as they work, making sure the problems are done correctly, in that they are justifying their answers by showing their work in coming up with the answers for the “Unknown Factor” in each division problem assigned.
• During this time, the teacher will ask questions of the students to make sure they understand the concept of solving for the unknown factor to solve division problems.
• The teacher will also answer questions posed by the students to help them clarify any misconceptions they may have.

## Extend

### Differentiation

• Enrichment: Give advanced students more challenging problems with higher dividends and lower factors to solve.
• Support: Observe and monitor these students more closely. Get involved in helping the students solve the problems. Use of manipulatives show the students visually how to solve the problems.

## Review

### Assessment (10 minutes)

• The students will be assessed based on the comments and feedback received during the lesson about the problems and at the conclusion of the lesson.
• Check the assignment for correctness.

### Review and Closing (15 minutes)

• Bring the students back to the class meeting area.
• Ask for volunteers to share their answers and work done to complete the problems assigned.
• As the problems are reviewed in front of the class, the students will check their answers for accuracy.
• After each problem has been checked for accuracy, ask the class if there are any questions or comments on solving for the unknown factor in division problems.