In this lesson, students generate products using the number line model.
This model highlights the measurement aspect of multiplication and is a distinctly different representation of the operation. The order (commutative) property of multiplication is also introduced. Students are encouraged to predict products and to answer puzzles involving multiplication.
All About Multiplication
Grades: 3rd to 5th
Author: Grace M. Burton
- Counters for the number line (chips, markers, etc.)
- Number Lines
On the overhead projector or chalkboard, display a large number line and demonstrate with a counter how hops of 5 can be taken on the number line. You may wish to encourage students to count aloud as the hops are made. You might choose to introduce the equation notation 4 × 5 = 20, informally reading it as “Four hops of 5, and you land on 20.” After several examples with 5 as a factor, ask the students to determine what size hop to use next. Encourage the students to predict the products and to verify their predictions by moving a counter on the large number line. You may wish to provide children with a counter and individual number lines at their desks.
After allowing time of exploration, ask the students to predict the answers to questions such as “If I take 4 hops of 3, where will I land?”
Now give each student a piece of paper and ask them to make up 2 similar problems and trade them with a friend to solve using the number line. When the pairs have finished, call them together to discuss what they did. Encourage them to use the number line in their explanation.
Be sure students have the opportunity to explore different factors, such as:
2 × 3
4 × 4
3 × 6
7 × 2
and so on….
Then ask: “If I take 5 hops of 3, where will I land? How about if I take 3 hops of 5? Will this work every time?” Encourage them to explore the order property and state their findings. [In each case, the student should land on 15, because of the commutative property of multiplication.]
As a concluding activity, you may wish to pose puzzles such as “I am a number between 20 and 30. You say my name when you hop by 5’s. Who am I?” and encourage students to create and share similar problems.
Assessments and Extensions
- At this stage of the unit it is important for students to know how to:
- use the number line model to find products
- the order property of multiplication
- solve and create puzzles using the number line
- The guiding questions suggest ways to help you determine if students have achieved these objectives. You may want to add others that the conversations with the students suggest. The Class Notes Recording Sheet provides a form on which to document your observations about student understanding and skills. You may find this information useful when discussing progress toward learning targets with individual students.
- If you wish to display a collection of the student puzzles in a public place, ask students to copy the puzzle, write the answer, and tape it under the puzzle. They might want to send a written challenge to students from other classes to solve the puzzles.
Questions and Reflections
Questions for Students
1. What numbers did you land on when you hopped by 5?
[5, 10, 15, 20, etc.]
2. What numbers did you land on when you hopped by 3?
[3, 6, 9, 12, 15, etc.]
3. Were any of the numbers the same?
[15, 30, etc.]
- What extension activities would be appropriate for students?
- Which students had trouble using the number line? What instructional experiences do they need next?
- What adjustments would you make the next time you teach this lesson?
Objectives and Standards
- Use the number line model to find products.
- Solve and create puzzles using the number line.
- Investigate the order property of multiplication.