5 pumps, working 9 hours a day, can empty a tank in 3 days. How many hours a day should 6 pumps work in order to empty the tank in 1 day? Choose the correct choice.
A) 20 hours
B) 22.5 hours
C) 23 hours
D) 23.5 hours
E) 24 hours
Let the required hours needed be x   More pumps, less hours (Indirect proportion)   More Days, less hours (Indirect proportion)   Hence we can write as   (pumps)5:6   }::x:9   (days)3:1   =&gt;5*3*9=6*1*x   =&gt;x=45/2= 
<gadget id="calculator">45/2</gadget>
<output>45/2 = around 22.5</output>
&gt;22.5   ANSWER:22.5 hours
<result>B</result>
5 pumps, working 9 hours a day, can empty a tank in 3 days. How many hours a day should 6 pumps work in order to empty the tank in 1 day?