The owner of a company wanted to purchase a new machine for his factory. He found three types of machines:
1-The first machine works 30 Minutes then stops to cool down for 5 Minute and works again another 30 Minutes and so on.
2-The second machine works 60 minutes then stops for 10 Minutes to cool down and so on.
3-The third machine works 90 minutes takes 15 minutes to cool down and so on.
If each product needs 30 minutes to be completely finished by any machine and the machine could work only 8.5 hours per day, which machine should he buy and why?
March 31st, 2011 | Category: 
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The 30 minute and 60 minute machines will produce 14 products in 8 hours and 10 minutes but because of the need to rest, will not complete the 15th in the remaining 20 minutes. The 90 minute machine will complete 15 products in 8 hours and 30 minutes, so the third machine is the best buy.
You nailed it, Paul!
In 8.5 Hours (510 Minutes):
The 30 Min Machine produces 14 Units (35 Min * 14 = 490 Min).
The 60 Min Machine produces 14 Units (70 Min * 7 = 490 Min).
The 90 Min Machine produces 15 Units (105 Min * 3 + 30 Min + 30 Min = 510 Min).
So he should buy the 90 Min Machine.
You’re today’s winner.