This Number Talk is designed to develop fluency with addition and subtraction of multi-digit numbers. This Warm-up also gives students a chance to reason about numbers beyond 1,000. The understanding elicited here will be helpful later in the unit and throughout IM Grade 4 when students add and subtract fluently using the standard algorithm.
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 strategy.
Keep expressions and work displayed.
Repeat with each expression.
Student Task
Find the value of each expression mentally.
650+75
5,650+75
50,650+75
500,650+75
Sample Response
725: 75 is also 50+25 and 650+50=700 and 700+25=725
5,725: Five thousands is the only new part of this number and 75 is not going to change the thousands. So, the answer is 5,725.
50,725: Fifty thousand is the only new part of this number and 75 is not going to change the ten-thousands. So, the answer is 50,725.
500,725: Five-hundred thousand is the only new part of this number and 75 is not going to change the hundred-thousands. So, the answer is 500,725.
Activity Synthesis (Teacher Notes)
“Which parts of the number change when we add 75?” (Just the hundreds, tens and ones.)
“How do we know without adding if digits in a number are going to change?” (Because we are not adding more than 10 tens to any of the numbers and there's only 6 hundreds. We know the thousands are not going to change.)
Standards
Addressing
4.NBT.4·Fluently add and subtract multi-digit whole numbers using the standard algorithm.
4.NBT.B.4·Fluently add and subtract multi-digit whole numbers using the standard algorithm.
15 min
20 min
Knowledge Components
All skills for this lesson
No KCs tagged for this lesson
Ten Times As Much
10 min
Narrative
This Number Talk is designed to develop fluency with addition and subtraction of multi-digit numbers. This Warm-up also gives students a chance to reason about numbers beyond 1,000. The understanding elicited here will be helpful later in the unit and throughout IM Grade 4 when students add and subtract fluently using the standard algorithm.
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 strategy.
Keep expressions and work displayed.
Repeat with each expression.
Student Task
Find the value of each expression mentally.
650+75
5,650+75
50,650+75
500,650+75
Sample Response
725: 75 is also 50+25 and 650+50=700 and 700+25=725
5,725: Five thousands is the only new part of this number and 75 is not going to change the thousands. So, the answer is 5,725.
50,725: Fifty thousand is the only new part of this number and 75 is not going to change the ten-thousands. So, the answer is 50,725.
500,725: Five-hundred thousand is the only new part of this number and 75 is not going to change the hundred-thousands. So, the answer is 500,725.
Activity Synthesis (Teacher Notes)
“Which parts of the number change when we add 75?” (Just the hundreds, tens and ones.)
“How do we know without adding if digits in a number are going to change?” (Because we are not adding more than 10 tens to any of the numbers and there's only 6 hundreds. We know the thousands are not going to change.)
Standards
Addressing
4.NBT.4·Fluently add and subtract multi-digit whole numbers using the standard algorithm.
4.NBT.B.4·Fluently add and subtract multi-digit whole numbers using the standard algorithm.