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OG16- DS 132

This topic has 4 expert replies and 1 member reply
amina.shaikh309 Senior | Next Rank: 100 Posts Default Avatar
Joined
23 Apr 2016
Posted:
31 messages

OG16- DS 132

Post Sat Aug 13, 2016 2:17 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])

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    Post Sat Aug 13, 2016 6:32 am
    See Mitch's solution here: http://www.beatthegmat.com/statistics-t62123.html

    Cheers,
    Brent

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    duahsolo Newbie | Next Rank: 10 Posts Default Avatar
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    Posted:
    7 messages
    Post Mon Aug 15, 2016 4:57 am
    amina.shaikh309 wrote:
    Statement (1) - not sufficient because we don't have any information on the # of books and their page numbers on the LOWER shelf

    Statement (2) - not sufficient because we don't have any information on the # of books and their page numbers on the UPPER shelf

    Together(1) and (2)
    We now have 49 page numbers (i.e., 49 books) and the median number will be the 25th (i.e.,the middle number) page number after the page numbers have been arranged/ordered from the least to the greatest page number (or vice versa).


    So we have 1st, 2nd, 3rd,,,24th <=400, 25th=400, 26th=475, 27th >=475, ..., 49th

    the middle number will be 400, sufficient.

    Answer: C

    GMAT/MBA Expert

    Post Mon Aug 15, 2016 8:16 am
    120) A certain bookcase has 2 shelves of books. On the upper shelf, the book with the greatest number of pages has 400 pages. On the lower shelf, the book with the least number of pages has 475 pages. What is the median number of pages for all of the books on the 2 shelves?

    1) There are 25 books on the upper shelf.

    2) There are 24 books on the lower shelf.

    Solution:

    We are given that a bookcase has 2 shelves of books. We are also given that the book with the greatest number of pages on the upper shelf has 400 pages and that the book with the least number of pages on the lower shelf has 475 pages. This tells us that all of the books on the upper shelf have fewer pages than all of the books on the lower shelf.

    We must determine the median number of pages of the books on the two shelves. Thus, if we were to order books on both shelves from the books with the least numbers pages to the books with the greatest number of pages, we must determine the number of pages in the middle book.

    Statement One Alone:

    There are 25 books on the upper shelf.

    Using the information in statement one, we know that the 25th book on the top shelf, when the books are ordered by the least number of pages to the greatest number of pages, has 400 pages. However, without knowing the number of books on the lower shelf, we still cannot determine the median number of pages for all the books on the two shelves. Statement one alone is not sufficient to answer the question. We can eliminate answer choices A and D.

    Statement Two Alone:

    There are 24 books on the lower shelf.

    Using the information in statement two, we know that the first book on the bottom shelf, when the books are ordered by the least number of pages to the greatest number of pages, has 475 pages. However, we still cannot determine the median number of pages for all the books on the two shelves. Statement two alone is not sufficient to answer the question. We can eliminate answer choice B.

    Statements One and Two Together:

    From statements one and two we know that there are a total of 49 books on the two shelves. Thus, we can determine which book, when the books are ordered by least number of pages to the greatest number of pages, is the median. To determine the median book we can follow the rule:

    If a set of numbers is in numerical order and has n terms and if n is odd, the median is the value at the (n+1)/2 position.

    position of median = (49 + 1)/2

    position of median = 25

    Thus, the 25th book is the median.

    From our two statements we also know that the book with the greatest number of pages on the upper shelf has 400 pages, and the book with the least number of pages on the lower shelf has 475 pages. This means that all the books on the upper shelf have fewer pages than the books on the lower shelf. So if we ordered the books on both shelves from the least number of pages to the greatest number of pages, we see that the book on the top shelf, with the greatest number of pages, or the 25th book, would be the median. Since we know that the 25th book has 400 pages, we know the median is 400 pages.

    Answer: C

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    Post Fri Aug 19, 2016 3:06 pm
    Brent@GMATPrepNow wrote:
    See Mitch's solution here: http://www.beatthegmat.com/statistics-t62123.html

    Cheers,
    Brent
    I'm starting to think I should just write a question recognition bot that can do this for any OG problem Very Happy

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    Post Fri Aug 19, 2016 4:54 pm
    Matt@VeritasPrep wrote:
    Brent@GMATPrepNow wrote:
    See Mitch's solution here: http://www.beatthegmat.com/statistics-t62123.html

    Cheers,
    Brent
    I'm starting to think I should just write a question recognition bot that can do this for any OG problem Very Happy
    Does not compute!!!!!

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