Matt is showing his work in simplifying (6.2 − 1.6) − 4.4 + 7.8. Identify any error in his work or reasoning.

Step 1: (6.2 − 1.6) − 4.4 + 7.8
Step 2: 6.2 + (− 1.6 − 4.4) + 7.8 (commutative property)
Step 3: 6.2 − 6 + 7.8
Step 4: −14 − 6 = 8 (commutative property)
Step 5: 14 − 6 = 8

Question

Matt is showing his work in simplifying (6.2 − 1.6) − 4.4 + 7.8. Identify any error in his work or reasoning. 

Step 1: (6.2 − 1.6) − 4.4 + 7.8
Step 2: 6.2 + (− 1.6 − 4.4) + 7.8 (commutative property)
Step 3: 6.2 − 6 + 7.8
Step 4: −14 − 6 = 8 (commutative property)
Step 5: 14 − 6 = 8

3mar · Answer

Which one did you pick?

radar · Answer

Something wrong happened in the transition from Step 3. to Step 4   what was it???>

skyerose · Answer

it was in step 2

radar · Answer

Step 2, and 3 are correct.  Matt simply combined the negative values.  Step 4 is incorrect, he used the wrong sign when combining the positive values.