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# M19-28

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Math Expert
Joined: 02 Sep 2009
Posts: 43829

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16 Sep 2014, 00:06
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Difficulty:

35% (medium)

Question Stats:

77% (01:22) correct 23% (01:40) wrong based on 138 sessions

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At 15:00 there were 20 students in the computer lab. At 15:03 and every three minutes after that, 3 students entered the lab. If at 15:10 and every ten minutes after that 8 students left the lab, how many students were in the computer lab at 15:44 ?

A. 7
B. 14
C. 25
D. 27
E. 30
[Reveal] Spoiler: OA

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Math Expert
Joined: 02 Sep 2009
Posts: 43829

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16 Sep 2014, 00:06
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Official Solution:

At 15:00 there were 20 students in the computer lab. At 15:03 and every three minutes after that, 3 students entered the lab. If at 15:10 and every ten minutes after that 8 students left the lab, how many students were in the computer lab at 15:44 ?

A. 7
B. 14
C. 25
D. 27
E. 30

During the 44 minutes between 15:00 and 15:44 $$\frac{42}{3} = 14$$ groups, 3 students each, entered the lab and $$\frac{40}{10} = 4$$ groups, 8 students each, left the lab. Thus, the number of students in the lab grew by $$14*3 - 8*4 = 10$$.

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Manager
Joined: 01 Sep 2016
Posts: 207
GMAT 1: 690 Q49 V35

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12 Aug 2017, 01:41
I think this is a high-quality question and I agree with explanation. in love with this question. AMAZING
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Intern
Joined: 24 Oct 2016
Posts: 29

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08 Oct 2017, 22:20
This is a high quality question.

Posted from my mobile device
Re: M19-28   [#permalink] 08 Oct 2017, 22:20
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# M19-28

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