bh10503 wrote:

10 machines work at constant rate and working together, they complete a job in 16 hrs. How mny hrs needed if only 8 machines work together to complete a job?

18

20

22

24

26

My take is B (20). The explaination as follows.

The way I understand this type of problems is by translating the problem into a ratio. In this problem as the number of machine increases, the number of hours required decreases and vice a versa. So the ratio has to be inversly proportional as follows

10/8 = x/16

So 8x = 160

and x = 20

I hope this makes sense.

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Thanks