iliavko wrote:

Can someone please post a full resolution for this thing? I dont get the algebra...

And why is B not sufficient???

Stmnt 2 is not sufficient.

The total cost of producing item X is equal to the sum of item X's overhead cost and production cost. If the production cost of producing X decreased by 5% in January, by what percent did the total cost of producing item X change in that same month?

(1) The overhead cost of producing item X increased by 13% in January.

(2) Before the changes in January, the overhead cost of producing item X was 5 times the production cost of producing item X.

Total Cost = Overhead Cost + Production Cost

We need to find the change in total cost. The question stem gives the percent decrease in production cost. But stmnt 1 gives the percent change in overhead cost. Without knowing the change in overhead cost, you cannot calculate the change in total cost. You cannot assume that there is no change in overhead cost.

Stmnt 2 tells us that if total cost was 120, 100 was overhead cost and production cost was 20. We know how 20 changed. But we also need to know whether and how 100 changed to know how 120 changed.

Hence, both statements are needed.

Answer (C)

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