Question 1171749
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20 men can dig a tank 40 feet long and 30 feet broad and 10 feet deep in 25 days. 
In how many days will 60 men dig a tank 90 feet long, 60 feet broad and 20 feet deep?
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<pre>
In first scenario, the volume of the tank is  40*30*10 = 12000 cubic feet.

and the rate of work is  {{{12000/(20*25)}}} = 24 cubic feet per day per man.



In second scenario, the volume of the tank is  90*60*20 = 108000 cubic feet.

and the rate of work is  {{{108000/(60*x)}}} = {{{1800/x}}} cubic feet per day per man, where x is an unknown number of days.



Assuming that the rate of work is the same in both scenarios, we have this equation

    24 = {{{1800/x}}},


which implies  x = {{{1800/24}}} = 75 days.    <U>ANSWER</U>
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Solved.