, Avg: 02:30 , 52%✓ SSC CGL 20201)Pipes A and B can fill a tank in 10 hours and 40 hours, respectively. C is an outlet pipe attached to the tank. If all the three pipes are opened simultaneously, it takes 80 minutes more time than what pipes A and B together take to fill the tank. A and B are kept opened for 7 hours and then closed and C was opened. C will now empty the tank in :
49 hours
Let x be time taken by A & B to fill the tank
then, \({1\over10}+{1\over40}={1\over x}\) , ⇒ x = 8 hours ;
All three simultaneously operating takes = \((8+{80\over60})={28\over 3}hours\);
\({1\over10}+{1\over40}-{1\over C}={3\over28}\) ; ⇒ C = 56 hours ;
Now A & B are opened for 7 hours then C is opened , let time taken to empty tank be y hours.
\({7\over10}+{7\over 40}-{x\over56}=0\) ; ⇒ x = 49 hours