Measure Figures Made from Prisms
10 min
Narrative
The purpose of this Number Talk is for students to reason about place-value relationships and the properties of multiplication. The elicited understandings and strategies will be helpful in later lessons and units when students multiply large numbers. In this unit, students produce and interpret multiplication expressions in terms of volume.
Launch
- Display one expression.
- “Give me a signal when you have an answer and can explain how you got it.”
- 1 minute: quiet think time
Teacher Instructions
- Record answers and strategies.
- Keep expressions and work displayed.
- Repeat with each expression.
Student Task
Find the value of each expression mentally.
- 6×2
- 6×2×10
- 6×20×10
- 60×20×10
Sample Response
- 12: I just know it.
- 120: I know 6×10=60 and 60×2=120.
- 1,200: I know 20×10=200 and 200×6=1,200.
- 12,000: 200×10×6=12,000, so it is 10 times as much as the previous product.
Activity Synthesis (Teacher Notes)
- “What patterns do you notice in the problems we solved?” (There is a 6 and a 2 in each product. There are also factors of 10, and the 6 and the 2 are sometimes multiplied by a factor of 10.)
- Consider asking:
- “Who can restate _____’s reasoning in a different way?”
- “Did anyone have the same strategy but would explain it differently?”
- “Did anyone approach the problem in a different way?”
Standards
- 5.NBT.2·Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.
- 5.NBT.A.2·Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.
20 min
15 min
Knowledge Components
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Measure Figures Made from Prisms
10 min
Narrative
The purpose of this Number Talk is for students to reason about place-value relationships and the properties of multiplication. The elicited understandings and strategies will be helpful in later lessons and units when students multiply large numbers. In this unit, students produce and interpret multiplication expressions in terms of volume.
Launch
- Display one expression.
- “Give me a signal when you have an answer and can explain how you got it.”
- 1 minute: quiet think time
Teacher Instructions
- Record answers and strategies.
- Keep expressions and work displayed.
- Repeat with each expression.
Student Task
Find the value of each expression mentally.
- 6×2
- 6×2×10
- 6×20×10
- 60×20×10
Sample Response
- 12: I just know it.
- 120: I know 6×10=60 and 60×2=120.
- 1,200: I know 20×10=200 and 200×6=1,200.
- 12,000: 200×10×6=12,000, so it is 10 times as much as the previous product.
Activity Synthesis (Teacher Notes)
- “What patterns do you notice in the problems we solved?” (There is a 6 and a 2 in each product. There are also factors of 10, and the 6 and the 2 are sometimes multiplied by a factor of 10.)
- Consider asking:
- “Who can restate _____’s reasoning in a different way?”
- “Did anyone have the same strategy but would explain it differently?”
- “Did anyone approach the problem in a different way?”
Standards
- 5.NBT.2·Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.
- 5.NBT.A.2·Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.