If a pipe A can fill a tank in 40 minutes and pipe B fill the same tank in 30 minutes. How long will it take for both pipes together to fill the tank?
a)17
b)16
c)15
d)120/7
e)13

• Time taken by both pipes together to fill the tank = 1/(1/40 +1/30) = 120/7 min
  
  so option d)
• 13 years agoHelpfull: Yes(6) No(0)
• in 1 minute water filled by both pipes together is 1/40+1/30=7/120
  
  to complete they will take 120/7
  
  
  
• 13 years agoHelpfull: Yes(3) No(0)
• d)120/7 minutes
• 13 years agoHelpfull: Yes(1) No(1)
• A'S 1 min. work=1/40
  B's 1 min work=1/30
  A+B 1nmin. work=1/10(1/4+1/3)=7/120
  time taken by A+B =120/7 ~17min.
• 7 years agoHelpfull: Yes(0) No(0)
• A can fill in 1 min = 1/40
  B can fill in 1 min = 1/30 so in 1 min A+B =1/40+1/30=7/120
  so 1/(7/120)=120/7
• 7 years agoHelpfull: Yes(0) No(0)
• a =40
  b=30
  Time taken by both pipes together to fill the tank= ab/(a+b)
  = 40*30/(40+30)
  = 120/7
• 3 years agoHelpfull: Yes(0) No(0)