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# Roger can read a book in k minutes. What part of the book can he read

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Current Student
Joined: 25 Jun 2014
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Roger can read a book in k minutes. What part of the book can he read [#permalink]

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19 Feb 2016, 09:45
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5% (low)

Question Stats:

82% (00:45) correct 18% (00:51) wrong based on 95 sessions

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Roger can read a book in k minutes. What part of the book can he read in 8 minutes? (k>8)

A) 8+k
B) 8/k
C) k/8
D) (k+ 8)/k
E) (k-8) / k
[Reveal] Spoiler: OA

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Manager
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Re: Roger can read a book in k minutes. What part of the book can he read [#permalink]

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19 Feb 2016, 12:07
If a book can be read in $$k$$ minutes, then the reading rate is $$\frac{1}{k}$$ books per minute. Therefore in 8 minutes

$$8*(\frac{1}{k})$$ books will be read

$$= \frac{8}{k}$$

An example with numbers to illustrate: if it takes Roger 16 minutes to read a book, that means he can read 1/16 of a book in a minute. So in 8 minutes he can read 8/16 of a book. This makes logical sense too; 16 minutes for a full book, 8 minutes for half a book. 1/2 = 8/16.
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Dave de Koos

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Re: Roger can read a book in k minutes. What part of the book can he read [#permalink]

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19 Feb 2016, 14:27
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Expert's post
Mesto wrote:
Roger can read a book in k minutes. What part of the book can he read in 8 minutes? (k>8)

A) 8+k
B) 8/k
C) k/8
D) (k+ 8)/k
E) (k-8) / k

Another approach is the input-out approach.

Let's say k = 24
That is, it takes 24 minutes to read the entire book.
So, in 8 minutes, Roger can read 1/3 of the book
So, we're looking for the answer choice that yields an OUTPUT of 1/3 when k = 24

A) 8+24 = 32 ELIMINATE
B) 8/24 = 1/3 KEEP
C) 24/8 = 3 ELIMINATE
D) (24+ 8)/24 = 32/24 = 4/3 ELIMINATE
E) (24-8) / 24 = 16/24 = 2/3 ELIMINATE

If you'd like more information on these approaches, we have some free videos:
- Variables in the Answer Choices - http://www.gmatprepnow.com/module/gmat- ... /video/933
- Tips for the Algebraic Approach - http://www.gmatprepnow.com/module/gmat- ... /video/934
- Tips for the Input-Output Approach - http://www.gmatprepnow.com/module/gmat- ... /video/935

Cheers,
Brent
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Re: Roger can read a book in k minutes. What part of the book can he read [#permalink]

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29 Nov 2017, 17:01
Mesto wrote:
Roger can read a book in k minutes. What part of the book can he read in 8 minutes? (k>8)

A) 8+k
B) 8/k
C) k/8
D) (k+ 8)/k
E) (k-8) / k

Since Roger’s rate is 1/k, he can read 1/k x 8 = 8/k of a book in 8 minutes.

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Scott Woodbury-Stewart
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Re: Roger can read a book in k minutes. What part of the book can he read   [#permalink] 29 Nov 2017, 17:01
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