standard_description: Apply properties of operations as strategies to multiply and divide. (Students need not use formal terms for these properties.) ^( )Examples: If 6 × 4 = 24 is known, then 4 × 6 = 24 is also known. (Commutative property of multiplication.) 3 × 5 × 2 can be found by 3 × 5 = 15, then 15 × 2 = 30, or by 5 × 2 = 10, then 3 × 10 = 30. (Associative property of multiplication.) Knowing that 8 × 5 = 40 and 8 × 2 = 16, one can find 8 × 7 as 8 × (5 + 2) = (8 × 5) + (8 × 2) = 40 + 16 = 56. (Distributive property.)
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have about the relationship between addition and subtraction. Each addition and subtraction equation represents the same part-whole relationship. These understandings help students develop fluency and will be helpful later in this lesson when students solve missing addend problems.
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 missing value mentally.
\(4 + \boxed{\phantom{1}} = 5\)
\(5 - \boxed{\phantom{1}} = 4\)
\(6 + \boxed{\phantom{2}} = 8\)
\(8 - \boxed{\phantom{2}} = 6\)
Student Response
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Activity Synthesis
“How can finding the missing value in the first equation help you with the second equation?" (I know that 1 more than 4 is 5, so I also know that 1 less than 5 is 4.)


aligns: no