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?
Choose the correct choice from the following answers:  A) 10  B) 11  C) 12  D) 13  E) 15
Let the required no of working hours per day be x.   More pumps , Less working hours per day (Indirect Proportion)   Less days, More working hours per day (Indirect Proportion)   pumps 4:3 and Days 1:2::8:x   Therefore, 4x1x(x)=3x2x8   X=(3x2x8)/4   X = 12.   Answer is 12.
<result>C</result>
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?