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Which expression uses the commutative property of addition and the associative property of multiplication to rewrite the expression [tex]$3 \cdot (2 \cdot 8) + 7$[/tex]?

A. [tex]$7 + (3 \cdot 2) \cdot 8$[/tex]
B. [tex][tex]$7 + 3 \cdot (16)$[/tex][/tex]
C. [tex]$3 \cdot (8 \cdot 2) + 7$[/tex]
D. [tex]$(3 \cdot 2) \cdot 8 + 7$[/tex]


Sagot :

Sure, let’s break down the steps for evaluating the given expression [tex]\( 3 \cdot (2 \cdot 8) + 7 \)[/tex] and identify the one that properly applies the commutative property of addition and the associative property of multiplication:

1. Starting Expression:
[tex]\[ 3 \cdot (2 \cdot 8) + 7 \][/tex]

2. Evaluate Inside Parentheses:
[tex]\[ 2 \cdot 8 = 16 \][/tex]

3. Substitute Back:
[tex]\[ 3 \cdot 16 + 7 \][/tex]

4. Perform Multiplication:
[tex]\[ 3 \cdot 16 = 48 \][/tex]

5. Add Constant:
[tex]\[ 48 + 7 = 55 \][/tex]

Thus, the original expression evaluates to 55.

Now, let's apply the commutative property of addition and the associative property of multiplication to rewrite the given expression:

1. Commutative Property of Addition allows us to rearrange terms:
[tex]\[ a + b = b + a \][/tex]
This property isn't immediately useful until we have an expression that involves addition besides the final constant, which we already have in the original form [tex]\(3 \cdot (2 \cdot 8) + 7\)[/tex].

2. Associative Property of Multiplication allows us to group factors differently:
[tex]\[ a \cdot (b \cdot c) = (a \cdot b) \cdot c \][/tex]
Applying this property, we get:
[tex]\[ 3 \cdot (2 \cdot 8) = (3 \cdot 2) \cdot 8 \][/tex]

Substitute back the evaluated expression:
[tex]\[ (3 \cdot 2) \cdot 8 + 7 = 6 \cdot 8 + 7 = 48 + 7 = 55 \][/tex]

Both expressions, [tex]\( 3 \cdot (2 \cdot 8) + 7 \)[/tex] and [tex]\( (3 \cdot 2) \cdot 8 + 7 \)[/tex], yield 55 when evaluated.

Thus, the expression that uses the commutative property of addition and the associative property of multiplication to rewrite the original expression [tex]\( 3 \cdot (2 \cdot 8) + 7 \)[/tex] is:

[tex]\[ (3 \cdot 2) \cdot 8 + 7 \][/tex]