9514 1404 393
Answer:
4 men
Explanation:
We presume the effort per "m" remains the same.
First project has effort/m of ...
(3 men)(7 h/day)(2 day)/(84 m) = (42/84) man·day/m = 1/2 man·day/m
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Then the number of men required for the second project is ...
(1/2) man·day/m × (256 m)/(8 h/day × 4 day) = (1·256)/(2·8·4) man = 4 man
It will take 4 men to complete the project in the given time.