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# There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar

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Intern
Joined: 27 Sep 2011
Posts: 13
There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar  [#permalink]

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28 Oct 2011, 23:07
6
4
00:00

Difficulty:

55% (hard)

Question Stats:

59% (01:38) correct 41% (01:58) wrong based on 176 sessions

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There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar books in my bookshelf. The books are randomly arranged in the shelf and not at all in the order of their type. What is the least number of books that must be drawn from the shelf in order to get 6 books of a particular type?

a) 20
b) 23
c) 25
d) 28
e) None of these

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Intern
Joined: 03 Oct 2011
Posts: 23
Re: There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar  [#permalink]

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29 Oct 2011, 06:14
3
Is the ans a ?

Suppose we need to draw 20 books.
Considering the worst case, If we remove all drama books that is 4 of them are gone out of 20 left with 16. Now suppose 5 of each novel, poetry and drama are drawn out from the shelf, that is 15 more books gone, so total 19 are taken out from the shelf and left with 1. Now the next 1 book which is pulled can be any of the three categories but it would definitely complete a set of 6 for one of the them.

Best case would be the first 6 we draw are of the same category. But if we pull 20 out atleast 1 of them would complete a set of 6.
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Re: There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar  [#permalink]

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01 Nov 2011, 14:53
Agreed.

This is a problem where you need to consider worst case:

1. Take out 4 Dramas.
2. Take 5 of each of the other 3, total of 15.
3. Next book you take will complete a set of 6.

Total is 4+15+1 = 20.

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Re: There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar  [#permalink]

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24 Oct 2017, 06:43
There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar books in my bookshelf. The books are randomly arranged in the shelf and not at all in the order of their type. What is the least number of books that must be drawn from the shelf in order to get 6 books of a particular type?

a) 20
b) 23
c) 25
d) 28
e) None of these

Let’s assume the worst case scenario. Let’s say we have drawn 5 novels, all 4 drama books, 5 poetry books, and 5 grammar books; we would have a total of 19 books drawn but still not have 6 books of one type. However, if we draw just one more book (which must be a novel, poetry, or a grammar book), we would have 6 books of one particular type. Thus, the least number of books that must be drawn is 20.

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Joined: 17 Sep 2017
Posts: 59
Re: There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar  [#permalink]

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07 Dec 2017, 09:35
I still do not understand. Can anyone please give more explaination on this question?
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Joined: 02 Sep 2009
Posts: 49964
Re: There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar  [#permalink]

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07 Dec 2017, 09:49
1
lichting wrote:
I still do not understand. Can anyone please give more explaination on this question?

There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar books in my bookshelf. The books are randomly arranged in the shelf and not at all in the order of their type. What is the least number of books that must be drawn from the shelf in order to get 6 books of a particular type?

a) 20
b) 23
c) 25
d) 28
e) None of these

The question asks to find the least number of books we should pick to guarantee that we have 6 books of one particular type. In such questions we should consider the worst case scenario which could happen. This would be if we pick all 4 drama books, 5 novel books, 5 poetry books, and 5 grammar books, so total of 19 books. In this case we still wouldn't have 6 books of one type. But the next, 20th, book we pick, be it novel, poetry or grammar book, would make 6 books for one of these types.

Check other Worst Case Scenario Questions from our Special Questions Directory to understand the concept better.
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Re: There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar &nbs [#permalink] 07 Dec 2017, 09:49
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# There are 9 novel books, 4 drama books, 12 poetry books and 7 grammar

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