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.

• Unit work is done in 1/4hrand 1/5hr
  So,in 4hr working alternatively total work is
  (1/4)*2+(1/5)*2=9/10
  Now work left is
  1-(9/10)=1/10
  This work is done by 1st pipe in
  4/10 hr=24 min.
  So total time taken is 4hr24min
• 8 years agoHelpfull: Yes(4) No(1)
• work is alternate so work done in two hours = 1/4+1/5=9/20 : work done in two hours
  in second two hours = 18/20
  and remaining work is 2/20
  so 1/4 will work for next alternate day
  = remaining work/time required to complete work =2/20*4/1=0.4
  that is o.4 of 1 hour = 24 minutes
  so total time required is 4 hr. 24 min.
• 8 years agoHelpfull: Yes(0) No(0)