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A certain machine drills 30 holes
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09 May 2015, 11:32
09 May 2015, 11:32
Expert Reply
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Question Stats:
88% (01:04) correct
11% (00:53) wrong based on 35 sessions
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A certain machine drills 30 holes in 8 minutes. At that constant rate, how many holes will 4 such machines drill in \(1\frac{1}{3}\) hours?
(A) 300
(B) 900
(C) 960
(D) 1,200
(E) 2,560
Kudos for the right answer and explanation
(A) 300
(B) 900
(C) 960
(D) 1,200
(E) 2,560
Kudos for the right answer and explanation
Re: GRE Math Challenge #90-A certain machine drills 30 holes
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17 Dec 2017, 21:52
17 Dec 2017, 21:52
1
sandy wrote:
A certain machine drills 30 holes in 8 minutes. At that constant rate, how many holes will 4 such machines drill in \(1\frac{1}{3}\) hours?
(A) 300
(B) 900
(C) 960
(D) 1,200
(E) 2,560
(A) 300
(B) 900
(C) 960
(D) 1,200
(E) 2,560
Here \(1\frac{1}{3}\) = 80minutes
Therefore we KNow-
Amount of work = Rate * Time
Amount of work = 30 holes
Rate = we need to find it
Time = 8 minutes
No. of machine = 1
so in first case
30 = 1 * R * 8
or Rate= \(\frac{30}{8}\)
Now for the 2nd case
Amount of work = We need to find out
Rate = \(\frac{30}{8}\)
No. of machine = 4
Time = 80 minutes
Therefore
A =R * T
A = 4 * \(\frac{30}{8}\) * 80
or A = 1200 holes
Re: GRE Math Challenge #90-A certain machine drills 30 holes
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18 Dec 2017, 02:26
18 Dec 2017, 02:26
1
We know the following formula :
# of outputs = (Rate)(Time)(# of machines)
We know that the outputs are 30 holes, time is 8 minutes and number of machine is 1.
Lets plug this
30 = (Rate)(8)(1)
Therefore the rate is 3,75 holes in one minute.
Now we are asking to find the number of outputs done by 4 machines in 1(1/3) hour.
Lets convert 1(1/3) this equals to 1h 20 minutes of 80 minutes.
Lets use again the same formula
# of outputs = (rate)(time)(# of machines)
# of outputs = (3,75)(80)(4)
# of outputs = 1200
# of outputs = (Rate)(Time)(# of machines)
We know that the outputs are 30 holes, time is 8 minutes and number of machine is 1.
Lets plug this
30 = (Rate)(8)(1)
Therefore the rate is 3,75 holes in one minute.
Now we are asking to find the number of outputs done by 4 machines in 1(1/3) hour.
Lets convert 1(1/3) this equals to 1h 20 minutes of 80 minutes.
Lets use again the same formula
# of outputs = (rate)(time)(# of machines)
# of outputs = (3,75)(80)(4)
# of outputs = 1200
