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# At a certain university, a new chemistry lab is built with three times

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Joined: 02 Sep 2009
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At a certain university, a new chemistry lab is built with three times  [#permalink]

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09 Mar 2017, 02:16
00:00

Difficulty:

15% (low)

Question Stats:

79% (02:13) correct 21% (01:59) wrong based on 140 sessions

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At a certain university, a new chemistry lab is built with three times the number of lab stations as the old chemistry lab. A professor plans to combine two existing chemistry classes in the new lab. If the first chemistry class took 1/3 of the original lab stations and the second chemistry class takes 1/5 of the new lab stations, what fraction of the lab stations in the new lab are taken when the two classes are combined?

A. 14/45

B. 1/3

C. 8/15

D. 31/45

E. 11/15

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Re: At a certain university, a new chemistry lab is built with three times  [#permalink]

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09 Mar 2017, 02:29
1
Bunuel wrote:
At a certain university, a new chemistry lab is built with three times the number of lab stations as the old chemistry lab. A professor plans to combine two existing chemistry classes in the new lab. If the first chemistry class took 1/3 of the original lab stations and the second chemistry class takes 1/5 of the new lab stations, what fraction of the lab stations in the new lab are taken when the two classes are combined?

A. 14/45

B. 1/3

C. 8/15

D. 31/45

E. 11/15

x ------- number of lab stations of the old chemistry lab
3x ------- number of lab stations of the new chemistry lab

x/3 ----- first chemistry class took 1/3 of the original lab stations
3x/5 ----- second chemistry class takes 1/5 of the new lab stations

fraction of the lab stations in the new lab taken when the two classes are combined
= ((3x)/5 + x/3)/3x
= ( 14x/5)/3x
= 14x/45x
= 14/45

Hence option A is correct
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Re: At a certain university, a new chemistry lab is built with three times  [#permalink]

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09 Mar 2017, 02:34
1
first class takes 1/3 of old lab
and old lab = new lab/3

so effectively first class takes (new lab/9 ) stations
second class takes (new lab/5)

total = n/9 + n/5 = 14/45..answer A
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Re: At a certain university, a new chemistry lab is built with three times  [#permalink]

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11 Mar 2017, 13:00
1st class took 1/3 of the old lab or (knowing new lab=3 old stations) 1/9 of the new. 1/9+1/5=14/45, hence, A
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Re: At a certain university, a new chemistry lab is built with three times  [#permalink]

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15 Mar 2017, 16:22
Bunuel wrote:
At a certain university, a new chemistry lab is built with three times the number of lab stations as the old chemistry lab. A professor plans to combine two existing chemistry classes in the new lab. If the first chemistry class took 1/3 of the original lab stations and the second chemistry class takes 1/5 of the new lab stations, what fraction of the lab stations in the new lab are taken when the two classes are combined?

A. 14/45

B. 1/3

C. 8/15

D. 31/45

E. 11/15

We are given that the new lab has 3 times as many lab stations as the old lab. If we let the number of stations in the old lab = d, then number of stations in the new lab = 3d.

Since one class takes (1/3)d lab stations of the old lab and the other class takes (1/5)(3d) = (3/5)d lab stations of the new lab, the total number of stations needed when the two classes are combined is (1/3)d + (3/5)d = (5/15)d + (9/15)d = (14/15)d.

Thus the fraction of lab stations that will be taken in the new lab is:

[(14/15)d]/(3d)

(14/15)/3

(14/15) x 1/3 = 14/45

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Re: At a certain university, a new chemistry lab is built with three times  [#permalink]

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15 Apr 2017, 09:52
ravisinghal wrote:
first class takes 1/3 of old lab
and old lab = new lab/3

so effectively first class takes (new lab/9 ) stations
second class takes (new lab/5)

total = n/9 + n/5 = 14/45..answer A

That is simple and great explanation many thanks
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Re: At a certain university, a new chemistry lab is built with three times  [#permalink]

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28 Dec 2017, 10:37
Is there a way to solve this using a matrix box?
Re: At a certain university, a new chemistry lab is built with three times   [#permalink] 28 Dec 2017, 10:37
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