Question

Tom is showing his work in simplifying (5.2 - 8.5) - 0.5 + 6.8. In which step did Tom make an error? (5 points)

Step 1:: (5.2 - 8.5) - 0.5 + 6.8
Step 2: 5.2 + (-8.5 - 0.5) + 6.8 (distributive property)
Step 3: 5.2 - 9 + 6.8
Step 4: 5.2 + 6.8 - 9 (commutative property)
Step 5: 12 - 9 = 3

Answer 1

Step 2; he wrote distributive instead of associative

Explanation:

Given the values A, B and C, the following expression is true about associative property

(A+B)+C = A+(B+C) [Associative property]

We can see that according to this property, we only regrouped the values without changing their positions.

Applying this in Tom's solution, we will find out that he made an error in step 2. The property he used was associative property not distributive property because all he did was to re-group the values with changing their positions.

From Step 1 and 2:

Step 1:: (5.2 - 8.5) - 0.5 + 6.8

Step 2: 5.2 + (-8.5 - 0.5) + 6.8 (Associative property)

Hence Tom made an error in step 2 where he wrote distributive instead of associative property.