One pipe fills in 4 hrs and another in 5hrs when they both work alternately
how much time will be taken to fill the tank.

• let A's 1 hr=1/4
  B's 1 hr=1/5
  (A+B)'s 2 hr job=1/4+1/5=9/20
  tank is full in 2^(20/9)=4.44
• 8 years agoHelpfull: Yes(1) No(1)
• 1/4+1/5+1/4+1/5=18/20
  
  1-18/20= 1/10
  
  4*1/10= 2/5 hr= 2/5*60= 24 min
  
  ans= 4 hr 24 min
• 7 years agoHelpfull: Yes(0) No(0)
• LCM approach 5,4 lcm is 20
  Now A takes 4 hrs so A does 5 unit of work(20/4) in 1hr
  Similarily B takes 5hrs so B does 4 unit of work(20/5) in 1hr
  Total unit is 20
  A and B fill tank alternately so A does 5unit in 1hr and B does 4 unit in 1hr so both do total of 9unit in 2hr so inorder to do 20 unit they will take (20×2)/9=40/9 hrs
• 7 years agoHelpfull: Yes(0) No(0)