This Number Talk encourages students to use place-value structure to mentally solve problems. The strategies elicited here will be helpful later in the lesson when students convert from milliliters to liters. When they divide by powers of 10, students look for and make use of place-value structure (MP7).
Launch
Display the first problem.
“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 problems and the work displayed.
Repeat with each problem.
Student Task
Find the value of each expression mentally.
1,400÷10
1,400÷100
1,400÷1,000
1,401÷1,000
Sample Response
140: The value of each digit in 140 is 101 the value of the corresponding digit in 1,400.
14: I divided 140 by 10 since dividing 1,400 by 100 is the same as dividing by 10 and dividing by 10 again.
1.4.: I divided the last product by 10.
1.401: The value of each digit is 1,0001 the value of the corresponding digit in 1,401.
Activity Synthesis (Teacher Notes)
Display: 1,401 and 1.401
“How are these numbers the same?” (They both have a 1, then a 4, then a 0, then a 1.)
“How are they different?” (The place values of the digits are different. The value of each digit in 1.401 is 1,0001 the value of the same digit in 1,401.)
Standards
Addressing
5.NBT.1·Recognize that in a multi-digit number, a digit in one place represents 10 times as much as it represents in the place to its right and 1/10 of what it represents in the place to its left.
5.NBT.A.1·Recognize that in a multi-digit number, a digit in one place represents 10 times as much as it represents in the place to its right and 1/10 of what it represents in the place to its left.
This Number Talk encourages students to use place-value structure to mentally solve problems. The strategies elicited here will be helpful later in the lesson when students convert from milliliters to liters. When they divide by powers of 10, students look for and make use of place-value structure (MP7).
Launch
Display the first problem.
“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 problems and the work displayed.
Repeat with each problem.
Student Task
Find the value of each expression mentally.
1,400÷10
1,400÷100
1,400÷1,000
1,401÷1,000
Sample Response
140: The value of each digit in 140 is 101 the value of the corresponding digit in 1,400.
14: I divided 140 by 10 since dividing 1,400 by 100 is the same as dividing by 10 and dividing by 10 again.
1.4.: I divided the last product by 10.
1.401: The value of each digit is 1,0001 the value of the corresponding digit in 1,401.
Activity Synthesis (Teacher Notes)
Display: 1,401 and 1.401
“How are these numbers the same?” (They both have a 1, then a 4, then a 0, then a 1.)
“How are they different?” (The place values of the digits are different. The value of each digit in 1.401 is 1,0001 the value of the same digit in 1,401.)
Standards
Addressing
5.NBT.1·Recognize that in a multi-digit number, a digit in one place represents 10 times as much as it represents in the place to its right and 1/10 of what it represents in the place to its left.
5.NBT.A.1·Recognize that in a multi-digit number, a digit in one place represents 10 times as much as it represents in the place to its right and 1/10 of what it represents in the place to its left.