SOLUTION: How do I explain how I can use the Commutative and associative properties to add 19+28+81 mentally?

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Question 909618: How do I explain how I can use the Commutative and associative properties to add 19+28+81 mentally?
Answer by JulietG(1812) About Me  (Show Source):
You can put this solution on YOUR website!
You could group them this way:
(19+81=100)+28 = 128 (associative)
or
81+19+28 = 1+9+8, carry the 1 mentally, 1+8+1+2 = 12. 12x + 8 = 128 (commutative)


The grouping is easier in this case.