Lesson 20
Products in the Hundredths Place
Lesson Purpose
Lesson Narrative
The purpose of this lesson is for students to find products of two decimal numbers where each decimal represents a number of tenths, using the place value reasoning and diagrams that were also useful for finding the product of a whole number and a decimal. Students explain why \(0.1 \times 0.1 = 0.01\) in the warm-up and this opens up one strategy for finding products like \(1.5 \times 0.7\). In particular, this can be rewritten as
\(\ (15 \times 0.1) \times (7 \times 0.1) = (15 \times 7) \times (0.1 \times 0.1)\).
So the value of \(1.5 \times 0.7\) is 105 hundredths or 1.05. A second approach uses area diagrams which students are familiar with from earlier lessons in this unit and from when they used them to find products of fractions. Decimals are an example of fractions and these diagrams are useful in this situation as well.
- Representation
- MLR8
Activity 1: Products of Tenths
Learning Goals
Teacher Facing
- Use diagrams and place value reasoning to interpret and evaluate products of two decimal numbers.
Student Facing
- Let’s multiply tenths by tenths.
Required Materials
Materials to Copy
- Small Grids
Required Preparation
Lesson Timeline
| Warm-up | 10 min |
| Activity 1 | 15 min |
| Activity 2 | 20 min |
| Lesson Synthesis | 10 min |
| Cool-down | 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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| Student Task Statements | docx | |
| Lesson Cover Page | docx | |
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| Teacher Guide | Log In | |
| Teacher Presentation Materials | docx | |
| Blackline Masters | zip |