Lesson 20
Will it Always Work? (optional)
Lesson Purpose
The purpose of this lesson is for students to explain how the product of
two numbers compares to one factor based on the size of the other factor.
Lesson Narrative
The goal of this optional lesson is to compare the size of a product to
the size of one factor, applying what students have learned in the last several lessons. They
make the comparisons and describe in general how to make comparisons using a strategy that makes
sense to them. No representation is provided or suggested so this gives students an opportunity
to think about the different methods they have learned, namely calculation, number lines and the
distributive property, and choose the one that makes sense in each situation.
- Representation
- MLR1
Learning Goals
Teacher Facing
-
Make generalizations about multiplying a whole number by a fraction greater than, less than, or equal to 1.
Student Facing
- Let’s make generalizations about multiplying a whole number by a fraction.
Required Materials
Materials to Gather
Required Preparation
CCSS Standards
Addressing
Lesson Timeline
| Warm-up | 10 min |
| Activity 1 | 20 min |
| Activity 2 | 15 min |
| Lesson Synthesis | 10 min |
| Cool-down | 5 min |
Teacher Reflection Questions
What questions did you ask today that helped students reason about the
size of a product without performing multiplication?
Suggested Centers
- Rectangle Rumble (3–5), Stage 5: Fraction Factors (Addressing)
- Rolling for Fractions (3–5), Stage 4: Multiply Fractions (Supporting)