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Machines

by greenwich » Thu Sep 09, 2010 2:21 pm
Machines X and Y produced identical bottles at different constant rates. Machine X, operating alone for 4 hours, filled part of a production lot; then machine Y, operating alone for 3 hours, filled the rest of this lot. How many hours would it have taken machine X operating alone to fill the entire production lot?
(1) Machine X produced 30 bottles per minute.
(2) Machine X produced twice as many bottles in 4 hours as machine Y produced in 3 hours.

Please provide answer with explanations.
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by Stuart@KaplanGMAT » Thu Sep 09, 2010 5:18 pm
greenwich wrote:Machines X and Y produced identical bottles at different constant rates. Machine X, operating alone for 4 hours, filled part of a production lot; then machine Y, operating alone for 3 hours, filled the rest of this lot. How many hours would it have taken machine X operating alone to fill the entire production lot?
(1) Machine X produced 30 bottles per minute.
(2) Machine X produced twice as many bottles in 4 hours as machine Y produced in 3 hours.

Please provide answer with explanations.
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by limestone » Thu Sep 09, 2010 5:30 pm
First, this is not a problem solving issue. This is a data suff issue.
Given information: there're some bottles to be made by machine X & Y. X worked alone 4 hours then Y worked alone 3 hours to finish the task.

(1) X produced 30 bottles per minute, so we can calculate how many bottle X can produce per hour. We can find out how many bottles X had produced in 4 hours but do not know how many bottles Y had produced in 3 hours. Therefore, we can not know what it would take for X to produce the no. of bottles Y produced in 3 hours. ---> Insuff

(2) the no. of bottles X produced in 4 hours doubles that of Y produced in 3 hours. So, if X produced K bottles, then Y produced K/2 bottles. It took X 4 hours to produce K bottles, therefore, it would take X 2 hours to produce K/2 bottles. In sum, it would take X: 4 + 2 = 6 hours to complete the task done by both X & Y as mentioned above. ---> Suff

So B wins.
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