A tank can be filled by two pipes A and B in 20 minutes and 60 minutes respectively. How many minutes will it take to fill the tank from empty state if B is used to fill first half and A and B together for the other half? A) 32.5 min B) 37.5 min C) 30 min D) 40 min

• B fills first half in 30 min.
  Then A and B together fill in 7.5 min.
  so ans is 37.5.
• 5 years agoHelpfull: Yes(2) No(0)
• in 1 minute A pipe=1/20 parts;
  in 1 minutes B pipe=1/60 parts;
  both in 1 minute;(1/20)+(1/60);==1/15 part;
  now 1/15 part in 1 minute then in 15 minutes tank will full;
  half tank time=7.5;
  now 30+7.5=37.5
• 4 years agoHelpfull: Yes(2) No(1)
• answer is 30 min
• 5 years agoHelpfull: Yes(0) No(3)
• Part filled by (A + B) in 1 minute =1/60+1/40=1/24
  Suppose the tank is filled in x minutes.
  Then, x/2(1/24 +1/40) = 1
  ==> x/2(5+3)/120=1
  ==> x/2*8/120=1
  ==> x=30 Ans.C
• 5 years agoHelpfull: Yes(0) No(3)