Two fill pipes A and B can fill a tank in 15 and 12 hours respectively . pipe B alone is kept open for 3/4 of time and both pipes are kept open for remaining time. In how many hours, the tank will be full?
[A] 18 h
[C] 16 h
[B] 11 h
[D] 10 h

• If total time taken is x hrs, then
  
  x*1/12 + (x/4)*(1/15) =1
  x(1/12 +1/60)=1
  x*(5+1)/60
  x= 10 hrs ... option D
• 12 years agoHelpfull: Yes(16) No(2)
• Work done by B = (1/12)*(3/4)= 1/16
  Reamainig work = 1-(3/4)= 1/4
  Reamainig work done by A & B = ((1/15)+(1/12))*(1/4)=3/80
  (1/16)+(3/80)= (8/80)=1/10
  ANS = (D)10h
  
• 10 years agoHelpfull: Yes(15) No(0)
• as b alone is open for 3/4 time.
  the remaining time is 1-3/4=1/4
  let x be the time required to fill tank
  3x/4(1/12)+1x/4(1/12+1/15)=1
  x/16+x/48+x/60=1
  lcm of 16,48,60=240
  (15x+5x+4x)/240=1
  24x=240
  x=10hrs.
  so tank is filled in 10hrs
• 10 years agoHelpfull: Yes(2) No(1)
• |-----------------|------------|
  9*x/4 (a+b) (only b)5*3x/4
  
  60lit
  
  15x/4+9x/4=60
  => x=10
• 10 years agoHelpfull: Yes(0) No(0)