3 pumps, working 8 hours a day, can empty a tank in 2 days. How many hours a day should 4 pumps work in order to empty the tank in 1 day?	Choose the correct choice from the following choices
A) 10
B) 12
C) 8
D) 15
E) 16
Explanation :   Let the required hours needed be x   More pumps, less hours (Indirect proportion)   More Days, less hours (Indirect proportion)   ⇒3 × 2 × 8 = 4 × 1 × x   ⇒ 3 × 2 × 2 = x   ⇒ x = 12 . Answer : Option 12
<result>B</result>
3 pumps, working 8 hours a day, can empty a tank in 2 days. How many hours a day should 4 pumps work in order to empty the tank in 1 day?