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# M25-21

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Math Expert
Joined: 02 Sep 2009
Posts: 51227

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16 Sep 2014, 00:23
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5
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Difficulty:

5% (low)

Question Stats:

82% (01:08) correct 18% (00:58) wrong based on 295 sessions

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In a certain collection of books there are 30 books in hard cover that contain more than 100 pages. If 15 percent of the books that contain more than 100 pages are in hard cover, how many books contain more than 100 pages but are not in hard cover?

A. 60
B. 90
C. 170
D. 180
E. 200

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Math Expert
Joined: 02 Sep 2009
Posts: 51227

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16 Sep 2014, 00:23
Official Solution:

In a certain collection of books there are 30 books in hard cover that contain more than 100 pages. If 15 percent of the books that contain more than 100 pages are in hard cover, how many books contain more than 100 pages but are not in hard cover?

A. 60
B. 90
C. 170
D. 180
E. 200

15 percent of all books that contain more than 100 pages = 30. Hence, there are in all $$\frac{30}{15}*100 = 200$$ books that contain more than 100 pages. Of these 200 books, 30 are in hard cover. Therefore, $$200 - 30 = 170$$ books that contain more than 100 pages but are not in hard cover.

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Joined: 11 Feb 2015
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26 Jun 2018, 08:35
It is given that 30 books are in hard cover that contain more than 100 pages. Using this information and knowing that this constitutes 15 percent, we can find the total books as 30 divided by 15% will give us the total books = 200 books. We can subtract the 30 from 200 to get the final answer as 170; i.e. the number books contain more than 100 pages but are not in hard cover:-

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2018-06-26_22-00-08.jpg [ 32.33 KiB | Viewed 1547 times ]

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Manish

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Joined: 12 Dec 2015
Posts: 132

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26 Jun 2018, 13:30
In a certain collection of books there are 30 books in hard cover that contain more than 100 pages. If 15 percent of the books that contain more than 100 pages are in hard cover, how many books contain more than 100 pages but are not in hard cover?

A. 60
B. 90
C. 170
D. 180
E. 200

Ans: C
T*15% = h
=> (h+s)*15% = h
=> (30+s)*15/100 = 30
=> 30+s = 200
=> s = 170
Re: M25-21 &nbs [#permalink] 26 Jun 2018, 13:30
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# M25-21

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