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Machine A can do a job in 12 hours at a constant rate and machine A do
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03 Nov 2016, 00:28
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Machine A can do a job in 12 hours at a constant rate and machine A do the job in 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone? A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs
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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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03 Nov 2016, 00:38
Machine A worked for 4 hours => completed 1/3rd of the work. Machine B does the work at 2/3 rate of A => time taken by B to complete = \(\frac{3}{2} *12\) = 18 hours.
B needs to complete 2/3rd of the work. Let time taken be x
\(\frac{1}{18} * x =\frac{2}{3}\) x = 12
Option A



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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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03 Nov 2016, 08:06
MathRevolution wrote: Machine A can do a job in 12 hours at a constant rate and machine A do the job in 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone?
A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs Let total work be 36 Efficiency of A = 3 Efficiency of B = 2 A works for 4 hours so it completes 12 units, hence work left is 24 units Since B does 24 units , time required by it is 24/2 = 12 Hence, Correct answer is (A)..
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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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06 Nov 2016, 23:51
==> Machine A works for 12 hours, but only did 4 hours, which is 1/3 of the job. Then, 2/3 of the job remains. Since the power of B is 2/3 of A’s, it takes 12 hours for B to do the remaining job. Hence, the answer is A. Answer: A
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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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06 Mar 2018, 02:52
MathRevolution wrote: Machine A can do a job in 12 hours at a constant rate but machine A do the job for 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone?
A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs Isn't this wording more appropriated?



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Machine A can do a job in 12 hours at a constant rate and machine A do
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06 Mar 2018, 07:55
MathRevolution wrote: Machine A can do a job in 12 hours at a constant rate and machine A do the job in 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone?
A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs MvArrow , I got confused, too: Machine A can do a job in 12 hours at a constant rate. Machine A works for 4 hours. Machine B, working at a constant rate, can do the same job at 2/3 the rate of machine A. If machine B does the rest of the job alone, how many hours does it take for Machine B to finish? Amount of work completed by Machine A?Work = 1 job Rate of A: \(\frac{1Job}{12hrs}=\frac{1}{12}\)Time that Machine A worked: 4 hours Amount of work Machine A completes: \(W = R * T\) \(W = \frac{1}{12} * 4=\frac{4}{12}=\frac{1}{3}\) of Work finished Work remaining for B: \(\frac{2}{3}\)B's rate? B is slower than A B's rate is \(\frac{2}{3}\) the rate of (= multiply) A B's rate: \((\frac{1}{12}*\frac{2}{3})=\frac{2}{36}=\frac{1}{18}\) = rate of B Time needed for B to finish work remaining?\(\frac{2}{3}\) of work remains \(R * T= W\), so \(T = \frac{W}{R}\)Time for B: \(\frac{\frac{2}{3}}{\frac{1}{18}}=(\frac{2}{3}*\frac{18}{1})=12\) hours Answer A



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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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19 Mar 2018, 02:29
MathRevolution wrote: Machine A can do a job in 12 hours at a constant rate and machine A do the job in 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone?
A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs Please correct the wording here. What is the question trying to say? Bunuel



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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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18 Jun 2018, 05:50
generis wrote: MathRevolution wrote: Machine A can do a job in 12 hours at a constant rate and machine A do the job in 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone?
A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs MvArrow , I got confused, too: Machine A can do a job in 12 hours at a constant rate. Machine A works for 4 hours. Machine B, working at a constant rate, can do the same job at 2/3 the rate of machine A. If machine B does the rest of the job alone, how many hours does it take for Machine B to finish? Amount of work completed by Machine A?Work = 1 job Rate of A: \(\frac{1Job}{12hrs}=\frac{1}{12}\)Time that Machine A worked: 4 hours Amount of work Machine A completes: \(W = R * T\) \(W = \frac{1}{12} * 4=\frac{4}{12}=\frac{1}{3}\) of Work finished Work remaining for B: \(\frac{2}{3}\)B's rate? B is slower than A B's rate is \(\frac{2}{3}\) the rate of (= multiply) A B's rate: \((\frac{1}{12}*\frac{2}{3})=\frac{2}{36}=\frac{1}{18}\) = rate of B Time needed for B to finish work remaining?\(\frac{2}{3}\) of work remains \(R * T= W\), so \(T = \frac{W}{R}\)Time for B: \(\frac{\frac{2}{3}}{\frac{1}{18}}=(\frac{2}{3}*\frac{18}{1})=12\) hours Answer A True... Wording of question is very poor. Hopefully GMAC never does such things. It is a relief that many have been confused by the wording, otherwise I was blaming myself.
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Re: Machine A can do a job in 12 hours at a constant rate and machine A do
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20 Jun 2018, 16:03
MathRevolution wrote: Machine A can do a job in 12 hours at a constant rate and machine A do the job in 4 hours. Machine B can do the same job at a 2/3 constant rate of machine A. If machine B does the rest job, what is the amount of hours done by machine B alone?
A. 12hrs B. 16hrs C. 24hrs D. 28hrs E. 32hrs The rate of Machine A is 1/12, and the rate of Machine B is 2/3 x 1/12 = 1/18. Machine A works for 4 hours, so it completes 4 x (1/12) = 1/3 of the job. When machine A stops working, 2/3 of the job remains to be finished by machine B. Thus, machine B works for (2/3)/(1/18) = 36/3 = 12 hours alone. Answer: A
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Re: Machine A can do a job in 12 hours at a constant rate and machine A do &nbs
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