A furniture manufacturer has two machines, but only one can be used at a time. Machine A is utilized during the first shift and Machine B during the second shift, while both work half of the third shift. If Machine A can do the job in 12 days working two shifts and Machine B can do the job in 15 days working two shifts, how many days will it take to do the job with the current work schedule?
(E) 7Source: GMAT Club Tests
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Kindly explain it.
Machine A needs 12 days * 2 shifts = 24 shifts to do the whole job;
Machine B needs 15 days * 2 shifts = 30 shifts to do the whole job;
In one day each machine works 1.5 shifts (3/2 shifts), and together, in one day, they are doing (3/2)/24+(3/2)/30=9/80 th of the whole, thus with the current work schedule they'll need 80/9=~9 days to do the whole job.
I am still a little confused with this question . I came across this on GMAT club test today.
How can we say that in one day , there are three shifts i.e first shift , second shift and third shift ? Cos it first says that , machine A takes 12 days to complete the job working 2 whole shifts
. Here , you take it to mean that two shifts comprise of one day. But when the question stem says "Machine A is utilized during the first shift and Machine B during the second shift, while both work half of the third shift"
, you are assuming , one day to comprise of - first shift , second shift and half of third shift .
I do not know what is it that I am missing out here . Appreciate if you can revert on this.