Question

Sandra is showing her work in simplifying (3.3 − 4.2) − 2.8 + 5.7. Identify any error in her work or reasoning. Step 1: (3.3 − 4.2) − 2.8 + 5.7 Step 2: 3.3 + (− 4.2 − 2.8) + 5.7 (distributive property) Step 3: 3.3 − 7 + 5.7 Step 4: 3.3 + 5.7 − 7 (commutative property) Step 5: 9 − 7 = 2

Answer 1

Sandra makes an error in second step reasoning .

Explanation:

We are given that Sandra is showing her work in simplifying

(3.3-4.2)-2.8+5.7

We have to find the error in her work or reasoning.

Step 1:(3.3-4.2)-2.8+5.7

Step 2:3.3+(-4.2)-2.8)+5.7

Reason: Associative property

Step 3:3.3-7+5.7

Step 4:3.3+5.7-7

Reason: Commutative property

Step 5:9-7=2

Hence, Sandra makes an error in second step reasoning .

Sandra uses distributive property instead of associative property in step 2.