Lesson 18
Use Whole Number Facts
Lesson Purpose
Lesson Narrative
The purpose of this lesson is for students to use whole number products to find products of a whole number and some tenths or hundredths. This builds on work from the previous lesson where students analyzed this strategy but did not represent the reasoning using equations. In this lesson, they write expressions and use the associative property of multiplication to justify why the strategy works (MP2, MP3). Students are not expected to name the associative property of multiplication each time they use it. In the second activity, the number of hundredths exceeds 10 but the same reasoning with whole number products applies. Because this product involves a decimal with both tenths and hundredths, it also makes sense to use the distributive property and work with tenths and hundredths separately and students analyze this strategy. Using distributive property to find products with decimals will be a main focus of the next lesson.
 Action and Expression
Learning Goals
Teacher Facing
 Multiply a whole number and a decimal using properties of operations and place value understanding.
Student Facing
 Let’s multiply whole numbers and decimals.
Required Preparation
Lesson Timeline
Warmup  10 min 
Activity 1  15 min 
Activity 2  20 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
Suggested Centers
 Target Numbers (1–5), Stage 8: Add Tenths or Hundredths (Addressing)
 Target Numbers (1–5), Stage 9: Subtract Tenths or Hundredths (Addressing)
Print Formatted Materials
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Additional Resources
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