4. A cistern can be filled in 9 hours but it takes 10 hours due to a leak in its bottom. If the cistern is full, then the time that the leak will take to empty it is:

• work done in one hour for filling the tank=1/9 per hr
  Similarly, Work done to empty the tank= 1/10 per hr
  so, When both work occuring simultaneously then work= (1/9-1/10) per hr
  i.e work=1/90 hr
  so, to empty the tank time required is : 90 hr ,Ans.90
• 13 years agoHelpfull: Yes(17) No(1)
• If A can fill a tank in x hours and B can fill a tank in y hours. Then the tank will be filled (empty) in hours
  Answer with Explanation:
  Time taken by A = 9 hours
  Time taken by B = 10 hours
  Time taken by A and B =
  = 90 hours.
  
• 13 years agoHelpfull: Yes(7) No(2)
• ans=90
  xy/(y-x);9*10/(10-1)=90hr;
• 13 years agoHelpfull: Yes(1) No(3)
• 90hrs
  1/9-1/10=1/90
  
  so 90 hrs it will take
• 13 years agoHelpfull: Yes(1) No(1)
• Let me try to put the solution with out using any variables such as x, y....etc.
  
  . At the start of the process the cistern was FULL
  . Can be filled in 9 hours
  . the cistern is emptied in 10 hours
  
  The Tank Capacity = LCM(9,10) = 90 units
  
  Work Done for filing = 90/9 = 10 units per hour
  Work Done for emptying = 90/10 = 9 units per hour (Negative Work)
  
  Net Work Done - 10 - 9 = 1 unit/hour
  
  The time that the leak will take to empty it = 90/1 = 90 hours (Ans)
• 9 years agoHelpfull: Yes(0) No(0)