Three pipes A,B & C are attached to a cistern. A & B can fill it in 20 & 30 minutes respectively, while C can empty it in 15 Minutes. If A,B & c are kept open successively for 1 min each, how soon would the cistern be filled. ??

Options are:
a) 180 min.
b)160 min.
c) 155 min.
d) 167 min.
e) 57 min.

• (1/20+1/30-1/15)=1/60. which is in 3 min.
  therefore, 1-(1/20+1/30) = 55/60. so, 55/60 of cistern filled in (3*55=165) min.
  now, 5/60 of the cistern remained to be filled.
  A will fill 1/20 portion in 1 min.
  remaining (5/60 - 1/20) or 1/30 in 1 min.
  therefore time reqd is. (165+1+1)= 167 min.
• 7 years agoHelpfull: Yes(1) No(0)
• 60 MIN NEED TO FILL THAT
  30 2
  20 60 3 =2+3-4=1
  15 -4
  A,B & c are kept open successively for 1 min each =60*3=180
  
• 9 years agoHelpfull: Yes(0) No(0)