Question

question 18 of 25
which shows the best use of the associative and commutative properties to make simplifying $2.4 + 13 - 5 + 3.6 + 7$ easier?
a. $(7 + 2.4 + 13) + 3.6 + (-5)$
b. $(2.4 + 3.6) + 13 + 7 + (-5)$
c. $2.4 + (-5) + 13 + (7 + 3.6)$
d. $(2.4 + 13) + (-5 + 3.6 + 7)$

Explanation:

Step1: Identify easy sum pairs

Notice $2.4+3.6=6$, $13+7=20$

Step2: Match to option

Option B groups these pairs:
$\boldsymbol{(2.4 + 3.6) + [13 + 7 + (-5)]}$

Step3: Verify simplification

Calculate grouped terms:
$2.4+3.6=6$, $13+7+(-5)=15$
Final sum: $6+15=21$, which is simplest.

Answer:

B. $(2.4 + 3.6) + [13 + 7 + (-5)]$