Six qualified workers can cast 100 tons of raw copper in 2 : PS Archive
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# Six qualified workers can cast 100 tons of raw copper in 2

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Six qualified workers can cast 100 tons of raw copper in 2 [#permalink]

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26 May 2008, 01:35
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Six qualified workers can cast 100 tons of raw copper in 2 hours. Two apprentices who work 2/3 as fast as a qualified worker are added to the group. Finally, the work is done. How much time has been saved due to the apprentices?
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26 May 2008, 01:51
6 people complete 100 in 2 hrs or 1 person completes 100/6 in 2 hrs so rate is 100/12
Now apprentice rate is 2/3 X 100/12 = 100/18

Now total time taken be T => 6X(100/12)XT + 2X(2/3)X(100/18) XT= 100
=> T/2 + (2/27)T = 1
=> T = 54/31 hrs

Time saved = 2- (54/31) = 8/31 hrs = 15 min approx
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26 May 2008, 11:44
2 apprentices combined is 2/3 as fast as 1 worker?

OR

each apprentice is 2/3 as fast as 1 worker?
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27 May 2008, 14:57
New time = (2*6*100)/(22/3*100) = 18/11hrs

22/3 - since each apprentice is 2/3 as fast as a regular worker, we are effewctively adding 6+2/3+2/3 = 22/3 workers and not 6+2 = 8

time saved = 2-18/11 = 4/11 hrs = 21.8 mins

Whats OA?
Re: PS: Saved Time   [#permalink] 27 May 2008, 14:57
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