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Roland and Felicia are testing circuit boards for wiring errors. Worki

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Bunuel
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Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink] New post   13 Feb 2019, 00:48
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Question Stats:

89% (01:10) correct 11% (01:52) wrong based on 94 sessions
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Roland and Felicia are testing circuit boards for wiring errors. Working together, they can test a circuit board in eight minutes. How many circuit boards can Felicia test in an hour
on her own?


(1) Felicia can test circuit boards twice as fast as Roland.

(2) If Roland and Felicia get their friend Cory to help them, they can all work together to test a circuit board in seven minutes.
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Archit3110
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Re: Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink] New post   19 Feb 2019, 05:00
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Bunuel wrote:
Roland and Felicia are testing circuit boards for wiring errors. Working together, they can test a circuit board in eight minutes. How many circuit boards can Felicia test in an hour
on her own?


(1) Felicia can test circuit boards twice as fast as Roland.

(2) If Roland and Felicia get their friend Cory to help them, they can all work together to test a circuit board in seven minutes.



#1
R+F/RF=1/8
so F=2R
so
3R/2R^2= 1/8
R= 12 mins
sufficient

#2
R+C+F/RCF= 1/7
rate of C and R not known
insuffcient
IMO A
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bharat8484
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Re: Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink] New post   07 Mar 2019, 01:35
Archit3110 wrote:
Bunuel wrote:
Roland and Felicia are testing circuit boards for wiring errors. Working together, they can test a circuit board in eight minutes. How many circuit boards can Felicia test in an hour
on her own?


(1) Felicia can test circuit boards twice as fast as Roland.

(2) If Roland and Felicia get their friend Cory to help them, they can all work together to test a circuit board in seven minutes.



#1
R+F/RF=1/8
so F=2R
so
3R/2R^2= 1/8
R= 12 mins
sufficient

#2
R+C+F/RCF= 1/7
rate of C and R not known
insuffcient
IMO A
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bharat8484
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Re: Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink] New post   07 Mar 2019, 01:38
can u please explain how did u get 3R/2R^2=1/8....?
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Archit3110
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Re: Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink] New post   07 Mar 2019, 01:52
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bharat8484 wrote:
can u please explain how did u get 3R/2R^2=1/8....?



bharat8484

Given
let rate of Roland =1/ R and Felicia = 1/F
so time taken by both working together
1/R + 1/F = 1/8
we get
(R+F)/RF=1/8--(1)

#1
given rate of F = 2R
so substitute in (1)
we get
3R/2R^2= 1/8
R= 12 mins
sufficient

Hope this helps.. :)
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bharat8484
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Re: Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink] New post   07 Mar 2019, 04:32
Archit3110 Oh yes i got it. Thank u so much.. :-)
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Re: Roland and Felicia are testing circuit boards for wiring errors. Worki [#permalink]
07 Mar 2019, 04:32
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