A can fill tank in 9 minutes, B can empty the tank in 18 minutes.. In what time the tank be filled, if both pipes work simultaneously? Choose one:
A) 14 minutes  B) 15 minutes  C) 16 minutes  D) 17 minutes  E) 18 minutes
Bigger no=18, Ratio=9:18=1:2   Time taken to fill the tank = 18/(2 - 1)= 
<gadget id="calculator">18/(2 - 1)</gadget>
<output>18</output>
18 minutes   ANSW18 minutesR:18 minutes
<result>E</result>
A can fill tank in 9 minutes, B can empty the tank in 18 minutes.. In what time the tank be filled, if both pipes work simultaneously?