Machine A can do a Certain Job in 12 Days Working 2 Full Shifts While Machine B can do the Same Job in 15 Days Working 2 Full Shifts.

Question: Machine A can do a certain job in 12 days working 2 full shifts while Machine B can do the same job in 15 days working 2 full shifts. If each machine A is working during the first shift, machine B is working during the second shift and both machines A and B are working half of the third shift, approximately how many days will it take machines A and B to do the job with the current work schedule?

1. 14
2. 13
3. 11
4. 9
5. 7

“Machine A can do a certain job in 12 days working 2 full shifts while Machine B can do the same job in 15 days working 2 full shifts. If each machine A is working during the first shift, machine B is working during the second shift and both machines A and B are working half of the third shift, approximately how many days will it take machines A and B to do the job with the current work schedule?”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book "GMAT Quantitative Review". GMAT Quant section consists of a total of 31 questions. To solve GMAT Problem Solving questions a student must have knowledge about a good number of qualitative skills. The GMAT quant topics in the problem-solving part require calculative mathematical problems that should be solved with proper mathematical knowledge.

Answer:

Machine A needs 12 days and 2 shifts to complete the whole job, this means machine A will take 24 shifts to complete the whole job.

Machine A needs 12 days * 2 shifts = 24 shifts to do the whole job

Now, Machine B needs 15 days and 2 shifts to complete the whole job, this means machine B will take 30 shifts to complete the whole job.

Machine B needs 15 days * 2 shifts = 30 shifts to do the whole job

In one day, machines work 1.5 shifts (means 3/2 shifts) and together in one day, they are doing (3/2) / 24 + (3/2) / 30 = 9/80th of the whole.

Thus, with the current work schedule they will need 80/9 = 9 days (approximately) to do the whole job.

Correct Answer: D

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