Two pipes A,B can fill a tank in 24 min. and 32 min. respectively. If both the pipes are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min.?

• work done by A => 18/24
  work done by B => x/32
  18/24 + x/32 = 1
  3/4 + x/32=1
  24+x=32 => x=8
  
  after 8 min b should be closed
• 12 years agoHelpfull: Yes(32) No(0)
• L.c.m of 24,32 is 96.
  let tank volume be 96 lit.then wrk dne by A=96/24= 4 lit/min.
  wrk dne by B= 96/32 = 3 lit/min.
  wrk dne by Both = 7 lit/min.
  7+7+7+7+7+7+7+7+(4*10)=96.
  so B shld b closed after 8 min.
  
• 11 years agoHelpfull: Yes(5) No(6)
• Let B be closed after x min. then,
  
  Part filled by (A+B) in x min. +part filled by A in (18-x) min = 1
  
  Therefore x*((1/24) + (1/32)) + (18-x)*(1/24) =1
  
  ==> (7x/96) + ((18-x)/24) =1.
  
  ==> 7x +4*(18-x) =96.
  
  Hence, be must be closed after 8 min.
• 10 years agoHelpfull: Yes(2) No(0)
• let total wrk to be done =96unit(lcm of 24,32)
  work done by A/min=(96/24)=4
  work done by B/min=(96/32)=3
  work done byA+B=(4+3)=7
  let tap B is closed after xmin
  7*x+(18-x)4=96
  solve and we will get x=8
• 10 years agoHelpfull: Yes(2) No(0)
• After 8 mins B should be closed.
  
  In 8 mins B can fill 25% of tank.
  In 18 mins A can fill 75% of tank.
  
  So if we close the pipe B after 8 minutes, the tank will be full in 18 minutes.
• 12 years agoHelpfull: Yes(1) No(7)
• 7 mins.
  In 18 mins A can fill the 75%. so A and B collectively filled the 25% of tank. If we open both the pipes then they will take (24+32)/2= 28 min to fill the tank. hence A and B simultaneously will take time to fill 25% of tank is = 28/4= 7 Mins.
• 12 years agoHelpfull: Yes(1) No(7)
• let b will be opened for x mins.
  (A+B)'s one minute work is (1/24+1/32)
  then(A+B)'s x minutes work is x(1/24+1/32)
  then remaining work should be completed by A alone in (18-x) minutes.
  x(1/24+1/32)+(18-x)(1/24)=1
  by solving above eqn we get x=8.
  
• 10 years agoHelpfull: Yes(1) No(0)
• after 8 minutes b should be closed
  
• 10 years agoHelpfull: Yes(0) No(1)
• a-24
  b-32
  after b close fill-?
  a alone 18 min-?
  24/18=4/3
  remeaning work =1/4*b
  1/4*32=8
  ans=8
• 8 years agoHelpfull: Yes(0) No(0)