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Working alone at its constant rate, machine K took 3 hrs to
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10 Jun 2020, 22:00
10 Jun 2020, 22:00
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Working alone at its constant rate, machine K took 3 hrs to produce 1/4 of the units produced last Friday. Then machine M started working and the two machines working simultaneously at their respective constant rates took 6 hrs to produce the rest of the units produced last Friday. How many hours would it have taken machine M working alone at its constant rate to produce all of the units produced last Friday?
A) 8
B) 12
C) 16
D) 24
E) 30
A) 8
B) 12
C) 16
D) 24
E) 30
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Re: Working alone at its constant rate, machine K took 3 hrs to
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11 Jun 2020, 07:27
11 Jun 2020, 07:27
2
bellatrix wrote:
Working alone at its constant rate, machine K took 3 hrs to produce 1/4 of the units produced last Friday. Then machine M started working and the two machines working simultaneously at their respective constant rates took 6 hrs to produce the rest of the units produced last Friday. How many hours would it have taken machine M working alone at its constant rate to produce all of the units produced last Friday?
A) 8
B) 12
C) 16
D) 24
E) 30
A) 8
B) 12
C) 16
D) 24
E) 30
Let's assign a nice value to the TOTAL number of units produced on Friday.
We want a number that works well with the given numbers in the question (1/4 and 6)
So let's say a TOTAL of 24 units were produced
Working alone at its constant rate, machine K took 3 hours to produce 1/4 of the units produced last Friday.
1/4 of 24 = 6
In other words, machine K took 3 hours to produce 6 units
Rate = output/time = 6/3 = 2
So, machine K produces 2 units PER HOUR
Then machine M started working and the two machines, working simultaneously at their respective constant rates, took 6 hours to produce the rest of the units produced last Friday.
24 - 6 = 18
So, when machine M starts helping, the two machines have 18 units to produce
Rate = output/time = 18/6 = 3
So, the COMBINED rate of the two machines is 3 units PER HOUR
We already know that machine K produces 2 units PER HOUR
3 - 2 = 1, so machine M produces 1 unit PER HOUR
How many hours would it have taken machine M, working alone at its constant rate, to produce all of the units produced last Friday?
Time = output/rate = 24/1 = 24
Answer: D
Cheers,
Brent
Re: Working alone at its constant rate, machine K took 3 hrs to
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29 Jul 2022, 00:52
29 Jul 2022, 00:52
Hello from the GRE Prep Club BumpBot!
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Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).
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