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Question 41615: Using the associative property of addition to write an expression
that is equivalent to the following expression.
(9 + 20) + 19
how can I write the expression. Thanks
Answer by tutorcecilia(2152)   (Show Source):
You can put this solution on YOUR website!
The associative property works with both addition and multiplication. It means that you can rearrange the parenthesis and still get the same answer. This does not work with division or subtraction.
(9 + 20) + 19 = 48
The parenthesis can be rearranged so that:
9 + (20 + 19) = 48
In the original problem you would first add (9+20)= 29 and then add 19 = 48.
In the rearranged problem you would first add (20+19) = 39 and then add 9 = 48
This also works with multiplication because the order of the operation doesn't matter in multiplication or addition. The order DOES matter in division and subtraction:
9 * (20 * 19) =9 * 380 = 3420
or, if we rearrange the parenthesis:
(9*20) * 19 = 180 * 19 = 3420
If this were a subtraction problem, the associative property would NOT work:
(9-20) -19 = -30
Rearranging the parenthesis:
9 -(20-19) = 9 - (1) = 8
You can see that when we try to apply the associative to a subtraction problem, we get a different answer. It would not work for division either.
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