A cistern is two third full of water.pipe A can fill the remaining part in 12 minutes and pipe B in 8 minutes. once the cistern is emptied, how much time will they take to fill it together completely?
(A)12minutes (B)12.5min (C)14.4min (D)10.2min (E)14.66min

• for A : 12 mint for one third of water filling
  hence it takes 36 mint to fill it completely
  for B: 8 mint to fill one third of cistern
  hence it takes 24 mint to fill it completely.
  for A & B :
  1/t = 1/36 + 1/24
  hence t = 14.4 mint
  so, ans is C
• 14 years agoHelpfull: Yes(10) No(0)
• for one third they take 12 &8 hrs
  so for complete filling A wil take 12*3=36 and B wil take 8*3=24
  so when r open they wil take
  1/t=1/36 + 1/24 =5/72
  hence t=72/5 =14.4 (C)
• 14 years agoHelpfull: Yes(5) No(0)
• 14.4 min
• 14 years agoHelpfull: Yes(2) No(0)
• A fill one third in 12 min i.e 1/3->12
  thus 1->12/(1/3)=36;
  B fill one third in 8 min i.e 1/3->8
  thus 1->8/(1/3)=24;
  Now 1/t= (1/36)+(1/24)
  t=14.4min
• 10 years agoHelpfull: Yes(0) No(0)