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There are 4 machines with the same work rate. If it took k

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by Max@Math Revolution » Thu Mar 01, 2018 2:40 am
[GMAT math practice question]

There are 4 machines with the same work rate. If it took k hours for 3 machines to work and did k-2 hours for 4 machines when working together, what is the value of k?

A. 4
B. 5
C. 6
D. 7
E. 8
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by mbawisdom » Thu Mar 01, 2018 6:20 am
Max@Math Revolution wrote:[GMAT math practice question]

There are 4 machines with the same work rate. If it took k hours for 3 machines to work and did k-2 hours for 4 machines when working together, what is the value of k?

A. 4
B. 5
C. 6
D. 7
E. 8
Total machine working hours will be the same for 3 machines and 4 machines.

Total machine hours with 3 machines = 3k
Total machine hours with 4 machines = 4(k-2)

3k = 4(k-2)
3k = 4k - 8
k = 8

Answer = (E) 8
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by Max@Math Revolution » Sun Mar 04, 2018 6:17 pm
=>

Work Amount = Number of machines * Work Rate * Time
If r is the machine's work rate, we have 3rk = 4r(k-2) or 3k = 4k -8.
Thus k = 8.

Therefore, E is the answer.

Answer: E
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by Scott@TargetTestPrep » Mon Jun 10, 2019 6:17 pm
Max@Math Revolution wrote:[GMAT math practice question]

There are 4 machines with the same work rate. If it took k hours for 3 machines to work and did k-2 hours for 4 machines when working together, what is the value of k?

A. 4
B. 5
C. 6
D. 7
E. 8
Let the rate of each machine be r. We can create the equation:

(3r)k = (4r)(k - 2)

3k = 4k - 8

8 = k

Answer: E

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