Question

Andrew is showing his work in simplifying −4.5 + 4.2 + 5.6 − 7.3. Identify any errors in his work or in his reasoning.

Step Work Reasoning
−4.5 + 4.2 + 5.6 − 7.3 Original problem
1 −4.5 + 4.2 + 5.6 + (−7.3) Additive inverse
2 −4.5 + (−7.3) + 4.2 + 5.6 Commutative property
3 [−4.5 + (−7.3)] + (4.2 + 5.6) Associative property
4 −11.8 + 9.8 Simplify
5 −21.6 Simplify
Step 1: He wrote −7.3 incorrectly as + (−7.3).
Step 2: He identified changing the order of the numbers as the commutative property, which is incorrect.
Step 3: He identified changing the grouping of the numbers as the associative property, which is incorrect.
Step 5: He simplified incorrectly.

Answer 1

5.

Explanation:

He simplified incorrectly:

-11.8 + 9.8 = -2, not -21.6.