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by paritosh_b » Thu Nov 04, 2010 9:49 pm
Came across this problem in one of the practice tests.

How many papers can Bill and Tim proofread in 60 minutes if they are working together?
(1) Bill can proofread twice as many papers as Tim in the same time period.
(2) Tim can proofread 30 fewer papers than Bill in 60 minutes.

A) Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.

B) Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.

C) Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.

D) Either statement BY ITSELF is sufficient to answer the question.

E) Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question,
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by bkk_marc » Fri Nov 05, 2010 1:13 am
Hi,

I think the answer is (C) for a few reasons:

First, I look at what is given: There are two elements (Bill and Tim), a time to complete a task (60 mins), and the function (Bill and Tim working together.

I know that there are information missing to answer this questions. I either need the individual work rate or any other information that can be plug in to this equation--> RATE x TIME = WORK

In (1) Bill can proofread twice as many papers as Tim in the same time period. This just gives us how fast Bill can read or the equation (Tim=Bill x 2) I don't think there is enough information here to solve because the amount of papers Tim can proofread can be any number.

Therefore now we know its either B,C,or E

in (2)Tim can proofread 30 fewer papers than Bill in 60 minutes. This also gives us how fast Tim can proofread, and giving the equation Tim = 30 - Bill. I don't think this is enough information because we don't know the exact numbers for Bill.

Now looking at both questions together we have T= 30 - B & T = 2B

So I used the plug-in method and got this--> 2B = 30 - B and solve and then B = 10. Now we can also plug in B to solve for T ( T = 2(10) ) and T = 20.

So we both Tim and Bill working together can proofread 30 papers in 60 mins


I am not sure if this is correct, but Im just showing you step by step how I was taught to approach these type of questions. [/i]
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by paritosh_b » Fri Nov 05, 2010 1:43 am
Indeed,C it is :)
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by diebeatsthegmat » Sun Nov 07, 2010 12:43 pm
bkk_marc wrote:Hi,

I think the answer is (C) for a few reasons:

First, I look at what is given: There are two elements (Bill and Tim), a time to complete a task (60 mins), and the function (Bill and Tim working together.

I know that there are information missing to answer this questions. I either need the individual work rate or any other information that can be plug in to this equation--> RATE x TIME = WORK

In (1) Bill can proofread twice as many papers as Tim in the same time period. This just gives us how fast Bill can read or the equation (Tim=Bill x 2) I don't think there is enough information here to solve because the amount of papers Tim can proofread can be any number.

Therefore now we know its either B,C,or E

in (2)Tim can proofread 30 fewer papers than Bill in 60 minutes. This also gives us how fast Tim can proofread, and giving the equation Tim = 30 - Bill. I don't think this is enough information because we don't know the exact numbers for Bill.

Now looking at both questions together we have T= 30 - B & T = 2B

So I used the plug-in method and got this--> 2B = 30 - B and solve and then B = 10. Now we can also plug in B to solve for T ( T = 2(10) ) and T = 20.

So we both Tim and Bill working together can proofread 30 papers in 60 mins


I am not sure if this is correct, but Im just showing you step by step how I was taught to approach these type of questions. [/i]
do you have another shorter and easier method to understand this?
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by bkk_marc » Sun Nov 07, 2010 7:41 pm
do you have another shorter and easier method to understand this?
Umm sure. I guess if you can create an equation for both (1) and (2) and see that there are two same variables, then you can solve for it.

But this is Data Sufficiency, so of course you go through the AD, BCE strategy. If (1) is not enough to answer the question.. then it has to be either B, C, or E.


I am not sure how else to explained this :( I am not an expert on explaining, but perhaps someone on here with credentials can explain better.

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