standard_description: Mentally add 10 or 100 to a given number 100–900, and mentally subtract 10 or 100 from a given number 100–900.
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have for addition and subtraction with 3 and 5. These understandings help students develop fluency and will be helpful later in this lesson when students will need to be able to create a yardstick with just the numbers 3 and 5.
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
Activity
Record answers and strategy.
Keep expressions and work displayed.
Repeat with each expression.
Student Facing
Find the value of each expression mentally.
\(3 + 5\)
\(5 - 3\)
\(5 - 3 + 5\)
\(3 + 5 + 3 + 3\)
Student Response
Teachers with a valid work email address can
click here to register or sign in
for free access to Student Response.
Activity Synthesis
“What other numbers can we make with 3 and 5? Think of two other numbers you can make. You can use as many threes and fives as you like and you may subtract and add.”


aligns: no