3 pumps working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day?  Answers.
A) 34	B) 77	C) 36	D) 49	E) 38
Explanation:   Let the required length be x meters   More men, More length built (Direct proportion)   Less days, Less length built (Direct Proportion)   \inline \fn_jvn \left.\begin{matrix} Men\: \: \: 20:35\\ Days\: 6:3 \end{matrix}\right\}::56:x   \inline \fn_jvn \therefore (20 x 6 x X)=(35 x 3 x 56) \inline \fn_jvn \Leftrightarrow \inline \fn_jvn x=\frac{35\times 3\times 56}{120} =49   Hence, the required length is 49 m.   Answer: 49
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3 pumps working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day?