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Manhattan Online test Question:

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Manhattan Online test Question:

by ash g » Sun Mar 02, 2008 6:12 pm
hi all,

My first post...and yes, me not happy so looking for some help.
Okee, so far I have given Gmatprep Test1 and gone through OG11. Thought of seeing how I fair in Manhattan free test. The 2nd question in Quant was a DS question which I got wrong but dont necessarily agree with the explantion.

Question
======

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

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

(2) Before the changes in January, the fixed cost of producing item X was 5 times the variable cost of producing item X.
+++++++++++++++++++++++++++++++
My answer - B. Their answer - C.
+++++++++++++++++++++++++++++++

They say S2 is insufficient as it doesnt give information about change in Fixed cost. But neither does the question stem. It doesnt mention that fixed cost changed. By GMATPrep standards/interpretation, I would by all means assume that it hasnt changed and mark B as the answer.

Where did I go wrong. Or is it that the question is not correctly worded.

ta,
ash
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Re: Manhattan Online test Question:

by hemanth28 » Sun Mar 02, 2008 6:23 pm
ash g wrote:hi all,

My first post...and yes, me not happy so looking for some help.
Okee, so far I have given Gmatprep Test1 and gone through OG11. Thought of seeing how I fair in Manhattan free test. The 2nd question in Quant was a DS question which I got wrong but dont necessarily agree with the explantion.

Question
======

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

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

(2) Before the changes in January, the fixed cost of producing item X was 5 times the variable cost of producing item X.
+++++++++++++++++++++++++++++++
My answer - B. Their answer - C.
+++++++++++++++++++++++++++++++

They say S2 is insufficient as it doesnt give information about change in Fixed cost. But neither does the question stem. It doesnt mention that fixed cost changed. By GMATPrep standards/interpretation, I would by all means assume that it hasnt changed and mark B as the answer.

Where did I go wrong. Or is it that the question is not correctly worded.

ta,
ash
T = F+V ...... Before Jan
now with condition 2 you know that F=5V
so T=6V ---before Jan.

But you know that in Jan V2=1.05V

so T2=F2+1.05V
(From what i understand you have assumed is T2=6V2 and come to a conclusion that option 2 alone is sufficiant,however it is no where mentioned that the fixed cost doesnt vary....which you are assuming)

So the cost of F2 is still missing isnt it?
So option (3) is right.
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by ash g » Sun Mar 02, 2008 6:37 pm
Thanks Hemant. My point is - I only have Information given in the question stem. Question stem doesnt mention about change in fixed cost.

Statement1 introduces that. If in this very question if statement2 would have appeared as statement1, I would have said S1 sufficient.

While looking at S2 and S2 alone alongwith question stem - to consider fixed cost not changed is an assumption. To consider fixed cost has changed is an assumption.

I think the wither the question is messed up or that I am having issues switching to non-OG material.
Thanks anyways.

Regards,
Ash
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by Stuart@KaplanGMAT » Sun Mar 02, 2008 6:54 pm
ash g wrote:Thanks Hemant. My point is - I only have Information given in the question stem. Question stem doesnt mention about change in fixed cost.

Statement1 introduces that. If in this very question if statement2 would have appeared as statement1, I would have said S1 sufficient.

While looking at S2 and S2 alone alongwith question stem - to consider fixed cost not changed is an assumption. To consider fixed cost has changed is an assumption.

I think the wither the question is messed up or that I am having issues switching to non-OG material.
Thanks anyways.

Regards,
Ash
You are 100% correct, but you're applying your thinking in the wrong way.

In DS, you should never assume anything. However, you've made the assumption that fixed cost hasn't changed, and that's what's tripping you up.

The stem says nothing at all about what happened to fixed cost, which means that we don't know if fixed cost has decreased, stayed the same or increased. Therefore, we need info about what happened to fixed cost in order to solve the problem.
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by simplyjat » Sun Mar 02, 2008 10:19 pm
As a rule of thumb, it the statements in a DS section introduce a new variable/equation; assume it to be required. :)
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