Q:
      
      
         
            
Taps X and Y can fill a tank in 30 and 40 minutes respectively.Tap Z can empty the filled tank in 60 minutes.If all the three taps are kept open for one minute each,how much time will the taps take to fill the tank?
         
       
      
      
      
          
      
      
          Answer & Explanation
         Answer: C) 24min         
         
Explanation: Given taps X and Y can fill the tank in 30 and 40 minutes respectively. Therefore,
 
part filled by tap X in 1 minute = 1/30
 
part filled by tap Y in 1 minute = 1/40
 
Tap Z can empty the tank in 60 minutes. Therefore,
 
part emptied by tap Z in 1 minute = 1/60
 
Net part filled by Pipes X,Y,Z together in 1 minute = [1/30 +1/40 - 1/60] = 5/120 = 1/24
 
i.e., the tank can be filled in 24 minutes.
 
 
       
      
      
      
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