Question

PLEASE HELP!!

Arlene is showing her work in simplifying −7.9 + 8.2 − 3.4 + 2.1. Identify any errors in her work or in her reasoning. Write feedback to Arlene explaining the mistake she made and how to correct her work.

Step Work Reasoning
−7.9 + 8.2 − 3.4 + 2.1 Original problem
1 −7.9 + 8.2 + (−3.4) + 2.1 Additive inverse
2 −7.9 + (−3.4) + 8.2 + 2.1 Associative property
3 (−7.9 + (−3.4)) + (8.2 + 2.1 Commutative property
4 −11.3 + 10.3 Simplify
5 −1 Simplify

Answer 1

In step 2 and step 3 reasoning mistakes

Explanation:

We are given that Arlene is showing her work in simplifying -7.9+8.2-3.4+2.1

We have to find error and correct the error made by Arlene in her work

Original problem : -7.9+8.2-3.4+2.1

Step 1: -7.9+8.2+(-3.4)+2.1

Additive inverse property

Step 2:-7.9+(-3.4)+8.2+2.1

Using Commutative property (commutative property a+b=b+a)

Step 3:(-7.9+(-3.4))+(8.2+2.1)

Using associative property (Associative property a+(b+c)=(a+b)+c))

Step 4: -11.3+10.3

By Simplification

Step 5:-1

By simplification

Arlene simplify in correct way but she is doing mistake in reasoning in step 2 and step 3.

Answer 2

There is nothing wrong with Arlene's math. Her answer is correct. The mistake is that she has cited the "associative property" where the "commutative property" should have been cited, and vice versa.

The associative property has to do with where you put parentheses. The commutative property has to do with what order the operands are in.