Question 563720
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3 people clean 1 office in 2 hours, so


3 people clean 1/2 of an office in 1 hour, so


1 person cleans 1/6 of an office in 1 hour, so


4 people clean 4/6 = 2/3 of an office in 1 hour, so


4 people clean 1 office in 3/2 of an hour, i.e. 1 hour 30 minutes.


John
*[tex \LARGE e^{i\pi} + 1 = 0]
My calculator said it, I believe it, that settles it
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