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Re: Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
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Statement 1:

Completely useless. Each of the first five chapters can be just 1 page long, or they can each be 50 pages long.

We just don't know: INSUFFICIENT

Statement 2:

Let just say the first three chapters each has 20 pages in the book and the rest of the chapters have only 19:

60/(300-12) is much less than 1/3

But if we say that each of the first three chapters has 100 pages and the rest of the 12 chapters has only 1:
300/(300+12) is much greater than 1/3

So still INSUFFICIENT

Statements 1 and 2

Because no exact relationship between the number of pages and the chapters are defined, we can still come up with scenarios in which Pat reads more or less than 1/3rd of the book while still satisfying Statements 1 and 2:

Less than 1/3:

(100+100+100+1+1)/(100+100+100+1+1+10*99)=23% (less than 33.3%)

More than 1/3:

(100+100+100+99+99)/(100+100+100+12*99)=33.4% (more than 33.3%)

we can further prove this:
5*x/(15*x) = 1/3
BUT
(3*y+3*x)/(15*x) is greater than 1/3 if we definte y>x
BUT
(3*y+3*1)/(15*x) is less than 1/3 if x is greater than 1 and y is greater than x

ANSWER: E.

What is the OA?
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Re: Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
Good one.

Statement 1: 5 chapters read doesn't give us anything since we don't know the # of pages per chapter.
Statement 2: Tells us that the # of pages read is >1/5 (assuming that the total # of pages in the first 3 chapters is slightly higher than in the others) , but we don't know whether the total is more than 1/3.

Statement 1 and 2 together: Doesn't help since we don't know # of pages in 4th and 5th chapter. So we are not sure if it will be >1/3 assuming that the # of pages is just slightly above 1/5 from Statement 2.

Answer (E)

Just to elaborate more picking some numbers

Obviously each statement alone is NOT sufficient

Now we have the following,

Say that there are 2 pages in each of the first 3 chapters, and we have 1 page for each of the remaining 12 chapters

We would then have a total of 6+2 =8 over a total of 18

8/18>=1/3? Yes, so this answers part of the question

Now we can try different numbers for the pages in each chapter. Thing is, as we have larger numbers then the fraction (8/18 in the first case) will decrease as the number of pages in the first 3 chapters will be a smaller part of the total number of pages. Therefore, from here we can already infer that we will also have a NO answer to this statement, and hence answer will be E

Hope it is now crystal clear
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Re: Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
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prude_sb wrote:
Pat is reading a book that has a total of 15 chapters. Has Pat read at least 1/3 of the pages in the book?

(1) Pat has just finished reading the first 5 chapters.
(2) Each of the first 3 chapters has more pages than each of the other 12 chapters in the book..


(1) Pat has just finished reading the first 5 chapters.
Each chapter can have variable number of pages. The number of pages in each chapter is not same
INSUFFICIENT

(2) Each of the first 3 chapters has more pages than each of the other 12 chapters in the book..
Good to know but how does it helps us. The number of pages can be X in the first 3 chapters and Y in the next 12 chapters
We cannot reach a a definite number to deduce what is 1/3 of (x+y)
INSUFFICIENT

MERGING BOTH STATEMENT
Again insufficient , because we still not know the total number of pages in the book

ANSWER:- E
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Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
prude_sb wrote:
Pat is reading a book that has a total of 15 chapters. Has Pat read at least 1/3 of the pages in the book?


(1) Pat has just finished reading the first 5 chapters.

(2) Each of the first 3 chapters has more pages than each of the other 12 chapters in the book.


DS21225


Remember: We don't know how many pages each chapter contains. One chapter may contain 1/3 of the pages and another may contain 1/15.

(1) Insufficient. We don't know how many pages the first 5 chapters consisted of.

(2) If the first 3 chapters has more pages than each of the other 12 chapters, this does not tell us any conclusive. INSUFFICIENT.

(1&2) Combined, we know Pat finished reading the first 5 chapters, and we are told the first 3 chapters has more pages than each of the 12 chapters.

We can't conclude that the first 5 chapters contained more than 1/3 of the book. INSUFFICIENT.

Answer is E.
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Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
BrentGMATPrepNow avigutman CrackVerbal, I tested a few cases and arrived at C. I could reason out that S1 and S2 individually are insufficient. Can you please suggest what should be the number picking strategy in such questions to ensure that we have possibly covered the ground that we need to?

Thank you!
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Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
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CrushTHYGMAT wrote:
BrentGMATPrepNow avigutman CrackVerbal, I tested a few cases and arrived at C. I could reason out that S1 and S2 individually are insufficient. Can you please suggest what should be the number picking strategy in such questions to ensure that we have possibly covered the ground that we need to?

Thank you!


CrushTHYGMAT it’s better to avoid testing specific numbers. Try to keep it a bit more abstract. When I combine the statements I just imagine two extremes for chapters 4 and 5 (since we know nothing about those two chapters, and the numbers of pages in those chapters are kind of important here). They could only have 1 page each or they could be the longest chapters by far (among chapters 4-15). Are you able to see how those cases lead to different answers?

Posted from my mobile device
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Re: Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
avigutman, I can definitely see why we can't have a certain number picking strategy that could be applied to such questions. The reason I got it wrong was that I didn't try two different cases. I rather tried different numbers of the same type - used a same number of pages in the first three chapters and a same number for remaining 12 chapters.

However, I now understand that why it is important for us to test extremes. Thank you so much for your response. Hope you have a great week. :)
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Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
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CrushTHYGMAT wrote:
BrentGMATPrepNow avigutman CrackVerbal, I tested a few cases and arrived at C. I could reason out that S1 and S2 individually are insufficient. Can you please suggest what should be the number picking strategy in such questions to ensure that we have possibly covered the ground that we need to?

Thank you!


CrushTHYGMAT

"Has Pat read at least 1/3 of the pages of the book?"

Let's try to analyze the Q.stem. To answer the question stem, you need to know the number of pages in the book. Nowhere in the statements or the question, have mentioned the number of pages in the book or a chapter. That opens up endless possibilities. As avigutman said, thinking about extreme values in these cases would be the best strategic approach.

For example, one chapter can have 1000 pages or more. Since there is no upper limit given for number of pages in a chapter anywhere in the problem, you have the liberty to think of these extremes.
As our answer to the Qstem is completely based on 1/3 of the pages of the book, a single chapter can bring a big difference in the number of pages in the book.

If you approach each statement with this thought process, you will easily get the answer without lengthy calculations.

Thanks,
Clifin J Francis,
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Re: Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
(1) Pat has just finished reading the first 5 chapters.
not sufficient, the distribution of the pages among th chapters is not known

(2) Each of the first 3 chapters has more pages than each of the other 12 chapters in the book.

assume that the book has 900 pages
avg number of pages for chapter would be 900/15=60
worst case is
61+61+61+57+60 = 300 not > 3000

E
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Re: Pat is reading a book that has a total of 15 chapters. Has Pat read at [#permalink]
I don't quite get the answer when using algebra?
The question is asking "Has Pat read at least 1/3 of the pages in the book", let a= no. of pages from first 3 chapters, let b= no. of pages from the remaining 12 chapters, the question can be translated to the following equation:

Is 3a+2b> 1/3 (3a+12b) ?
3a+2b >a+4b?
2a>2b?
a>b

From B we know, each of the first 3 chapters has more pages than each of the other 12 chapters in the book >>> a >b, so the equation should satisfy. It means Pat does read at least of 1/3 of the page.

Please let me know why this method is wrong, thanks a lot!

combining A and B, we know
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