<PRE><B>Question 760731</B>
12 engineers working together can build 30 identical cars in 6 days.
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Half as many engineers can build the same number in twice that time, so
6 engineers working together can build 30 identical cars in 12 days.
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Three times that many engineers can build the same 
number in one-third that time, so,
18 engineers working together can build 30 identical cars in 4 days.
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18 engineers working together can build half that number of cars
in half that time, so
18 engineers working together can build 15 identical cars in 2 days. 
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