Metric Conversion and Multiplication by Powers of 10
10 min
Narrative
In this Number Talk, students find products of a decimal number and a power of 10 and quotients of a whole number and a power of 10, the value of which is a decimal. This skill will be useful throughout the next several lessons as students convert between different metric units of measure and also specifically address how a whole or decimal number changes when it is multiplied or divided by a power of 10.
Launch
Display the first 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 students’ answers and strategies.
Keep the expressions and the work displayed.
Repeat with each expression.
Student Task
Find the value of each expression mentally.
100×1.5
1,000×1.5
15÷10
15÷100
Sample Response
150: It’s 100 and half of another 100.
1,500: It’s 1,000 and half of 1,000.
1.5: I pictured it as a fraction, 1015, which is equal to 1 and 5 tenths.
0.15: 15÷100=15×1001 and that is equal to 0.15.
Activity Synthesis (Teacher Notes)
“What is the same about the values of the expressions?” (There is a 1 and a 5 in each value.)
“What is different about the values of the expressions?”(Some of them are whole numbers and some are decimals.)
Standards
Addressing
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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Metric Conversion and Multiplication by Powers of 10
10 min
Narrative
In this Number Talk, students find products of a decimal number and a power of 10 and quotients of a whole number and a power of 10, the value of which is a decimal. This skill will be useful throughout the next several lessons as students convert between different metric units of measure and also specifically address how a whole or decimal number changes when it is multiplied or divided by a power of 10.
Launch
Display the first 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 students’ answers and strategies.
Keep the expressions and the work displayed.
Repeat with each expression.
Student Task
Find the value of each expression mentally.
100×1.5
1,000×1.5
15÷10
15÷100
Sample Response
150: It’s 100 and half of another 100.
1,500: It’s 1,000 and half of 1,000.
1.5: I pictured it as a fraction, 1015, which is equal to 1 and 5 tenths.
0.15: 15÷100=15×1001 and that is equal to 0.15.
Activity Synthesis (Teacher Notes)
“What is the same about the values of the expressions?” (There is a 1 and a 5 in each value.)
“What is different about the values of the expressions?”(Some of them are whole numbers and some are decimals.)
Standards
Addressing
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.