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) 33
B) 77
C) 26
D) 12
E) 99
Let the required number 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 :: 8 : x   Days	1	:	2   4 x 1 x x = 3 x 2 x 8   x =	(3 x 2 x 8)   (4)   x = 12.   Answer:12
<result>D</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?