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Re: Working alone at its constant rate, machine A can complete a job in 24 [#permalink]
Chaithraln2499 wrote:
How did we arrive at 48hours for machine B?


Machine A can complete a job in 24 hours.
If Machine B's rate is HALF that of machine A, it will take machine B TWICE as along as machine A to complete the job.

Similar example:
At a speed of 60 mph, it will take a car 3 hours to drive 180 miles.
If we HALVE the car's rate to 30 mph, it will take a car 6 hours (TWICE as long) to drive 180 miles.
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Re: Working alone at its constant rate, machine A can complete a job in 24 [#permalink]
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Output=Rate*time, if output of B= 1/2 of A, Work B= 0.5*24*Rate of A= 12* Rate of A, I get time as 12, what is it that I'm assuming wrongly?

GreenlightTestPrep wrote:
Chaithraln2499 wrote:
How did we arrive at 48hours for machine B?


Machine A can complete a job in 24 hours.
If Machine B's rate is HALF that of machine A, it will take machine B TWICE as along as machine A to complete the job.

Similar example:
At a speed of 60 mph, it will take a car 3 hours to drive 180 miles.
If we HALVE the car's rate to 30 mph, it will take a car 6 hours (TWICE as long) to drive 180 miles.
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Re: Working alone at its constant rate, machine A can complete a job in 24 [#permalink]
Chaithraln2499 wrote:
Output=Rate*time, if output of B= 1/2 of A, Work B= 0.5*24*Rate of A= 12* Rate of A, I get time as 12, what is it that I'm assuming wrongly?


The question doesn't tell us that output of B = 1/2 of A, it tells us that work rate of machine B is 1/2 that of machine A

The full question: Working alone at its constant rate, machine A can complete a job in 24 hours. The work rate of machine B is 1/2 that of machine A. If machine A works on the job for 6 hours and machine B completes the job, how long does it take machine B to finish the job?
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Re: Working alone at its constant rate, machine A can complete a job in 24 [#permalink]
1
Machine A rate = X

Machine B = X/2

A completes a job in 24 hours

Rate of A = 1/24

If A does a work in 6 hours, fraction of work done

1/24 = W/ 6

Which gives 1/4

That ultimately means 3/4 of work left to be done

If B's rate is 1/2 of A, rate for B will be 1/48
Time to complete 3/4 of work = 1/48 = 3/4 x 1/T

T = 36 hours.
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Re: Working alone at its constant rate, machine A can complete a job in 24 [#permalink]
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