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While working alone at their constant rates computer X can process 240 [#permalink]
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Updated on: 16 Dec 2014, 03:53
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85% (00:55) correct 15% (01:21) wrong based on 368 sessions
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While working alone at their constant rates computer X can process 240 files in 4 hours, and comp Y 240 files in 8 hrs. If all files processed by these comp. are the same size how long would it take the two comp. working at the same time at their respective constant rates , to process a total of 240 files? A. 2hrs B. 2hrs 20 min C. 2hrs 40 min D. 6hrs E. 6hrs 20 min i did as under X in one hour = 240/4 = 60 files Y in one hour = 240/8 = 30 fles X+ Y in one hour 60+30=90 files So together they will take (240/90)= 2 hours 40 minutes. So C is the answer. I do not know the OA. Am I right?
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Originally posted by Baten80 on 29 Mar 2011, 04:36.
Last edited by Bunuel on 16 Dec 2014, 03:53, edited 1 time in total.
Renamed the topic, edited the question and added the OA.



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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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29 Mar 2011, 04:49
Yes, your answer is correct. Btw, 240 files information is irrelevant here, as both do the same work, it can be regarded as 1 unit of work. In 1 hr, both finish = 1/8 + 1/4 = (1+2)/8 part of work So total in 8/3 hrs = 2 2/3 hrs = 2 hrs 40 min
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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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29 Mar 2011, 05:14
Baten80 wrote: While working alone at their constant rates computer X can process 240 files in 4 hours, and comp Y 240 files in 8 hrs. If all files processed by these comp. are the same size how long would it take the two comp. working at the same time at their respective constant rates , to process a total of 240 files?
2hrs 2hrs 20 min 2hrs 40 min 6hrs 6hrs 20 min
i did as under X in one hour = 240/4 = 60 files Y in one hour = 240/8 = 30 fles X+ Y in one hour 60+30=90 files So together they will take (240/90)= 2 hours 40 minutes. So C is the answer. I do not know the OA. Am I right? Computer 1 processes 60 files an hour Computer 2 processes 30 files an hour Combined they will process 90 files an hour For 240 files, they will take (240/9) hours ... which is 2h40m
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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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29 Mar 2011, 05:47
Baten80 wrote: While working alone at their constant rates computer X can process 240 files in 4 hours, and comp Y 240 files in 8 hrs. If all files processed by these comp. are the same size how long would it take the two comp. working at the same time at their respective constant rates , to process a total of 240 files?
2hrs 2hrs 20 min 2hrs 40 min 6hrs 6hrs 20 min
i did as under X in one hour = 240/4 = 60 files Y in one hour = 240/8 = 30 fles X+ Y in one hour 60+30=90 files So together they will take (240/90)= 2 hours 40 minutes. So C is the answer. I do not know the OA. Am I right? Yes, you are right. You have solved it by unitary method; 90 files > 1 hour 1 file > 1/90 hour 240 files > (1/90)* 240 hours
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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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06 Apr 2011, 07:25
X  60 files per hour Y  30 files per hour X & Y together  90 files per hour 90+90=180 We need 60 more So 60/90 of an hour i.e. 2/3 of an hour = 40 min So 2 hours and 40 min...



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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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11 Aug 2011, 06:42
X does 240 in 4hrs = 60 in 1 hr Y does 240 in 8hrs = 30 in 1hr X+Y = 90 in 1hr 240 in = 240/90 = 2.6666 hrs = 2hrs 40mins
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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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11 Aug 2011, 16:03
subhashghosh wrote: Yes, your answer is correct.
Btw, 240 files information is irrelevant here, as both do the same work, it can be regarded as 1 unit of work.
In 1 hr, both finish = 1/8 + 1/4 = (1+2)/8 part of work
So total in 8/3 hrs
= 2 2/3 hrs
= 2 hrs 40 min I like this approach. But can someone tell me why 3/8 was flipped to 8/3 to get the final answer?



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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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11 Aug 2011, 16:11
X 60 files/hour Y 30 files/hour
together , they will take 240/(60+30) hours to process 240 files
= 240/90 = 2hr 40 min



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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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11 Aug 2011, 16:25
Here we are considering work as 1 unit of work. X  does 1 unit of work in 4 hours => rate of x = 1/4 Y  does 1 unit of work in 8 hours =>rate of y = 1/8 together their rate is 1/4+1/8 = 3/8 work  same 1 unit of work = 1 time it will take do the unit work = 1/(3/8) = 8/3 hours Hope its clear now. aks1985 wrote: subhashghosh wrote: Yes, your answer is correct.
Btw, 240 files information is irrelevant here, as both do the same work, it can be regarded as 1 unit of work.
In 1 hr, both finish = 1/8 + 1/4 = (1+2)/8 part of work
So total in 8/3 hrs
= 2 2/3 hrs
= 2 hrs 40 min I like this approach. But can someone tell me why 3/8 was flipped to 8/3 to get the final answer?



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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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11 Aug 2011, 23:45
X in 1 hr = 60 and y in 1 hr = 30 files. in 2 hrs X + Y = 120 + 60 = 180 remaining = 60 hence in 40 mins X + Y = 40 + 20 = 60 thus 2:40 C is the cue.
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Re: While working alone at their constant rates computer X can process 240 [#permalink]
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05 Nov 2017, 08:21
Baten80 wrote: While working alone at their constant rates computer X can process 240 files in 4 hours, and comp Y 240 files in 8 hrs. If all files processed by these comp. are the same size how long would it take the two comp. working at the same time at their respective constant rates , to process a total of 240 files?
A. 2hrs B. 2hrs 20 min C. 2hrs 40 min D. 6hrs E. 6hrs 20 min The rate of computer X is 240/4 = 60 files in 1 hour and the rate of computer Y is 240/8 = 30 files in 1 hour, so the combined rate is 90 files in 1 hour. Thus, it takes 240/90 = 2 60/90 hours = 2 ⅔ hours = 2 hours and 40 minutes to complete 240 files when both computers work together. Answer: C
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Re: While working alone at their constant rates computer X can process 240
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