Question

Marcel made an error when he used the distributive property to solve the problem shown. Which sentence describes the error?

Answer 1

The answer to this is step 2 because they multiplied when they should of subtracted the 10 and the 12.

Answer 2

In Step 2, 90 should be multiplied by the quantity 10 – 12, not by 10.

Explanation:

Consider the provided expression.

`90\cdot x-90\cdot 12` when x=10

Solve the above expression as shown:

Step 1:

`90\cdot x-90\cdot 12=90(x-12)`

Step 2: Substitute x=10.

`90\cdot x-90\cdot 12=90(10-12)`

Step 3: Open the parenthesis.

`90\cdot x-90\cdot 12=900-1080`

Step 4: Simplify

`90\cdot x-90\cdot 12=-180`

From the above calculation we can say that the error is:

In Step 2, 90 should be multiplied by the quantity 10 – 12, not by 10.