Apply properties of operations as strategies to add and subtract.2 Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)
Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8. Add and subtract within 20.
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Khan - Commutative and Associative Laws of Addition Example using both the commutative and associative laws of addition (3:23) |
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Khan - Associative Law of Addition Review the associative law of addition with Sal (2:10) |
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Khan - Commutative Law of Addition Learn about the commutative law of addition (1:40) |
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