Three taps a b and c can fill a tank in 12 15 and 20 hrs respectivly if a is open all the time and b and c are open for one hour each alternately the tank will be full in

• a's 1 hr work = 1/12
  b's 1 hr work = 1/15
  c's 1 hr work = 1/20
  
  a is open all d time... b nd c open for alternate hrs...so a nd b opens at a time... a nd c opens at a time
  
  a+b's 1 hr work = 1/12 + 1/15 = 27/180 = 3/20
  a+c's 1 hr work = 1/12 + 1/20 = 32/240 = 2/15
  
  1st hr, a+b ll be opened --- so part of tank filled is = 3/20
  
  2nd hr -- a+c ll be opeed --- so part of tank filled is = 2/15
  
  In 6 hrs, a+b opened for 3 hr nd a+c opened for 3 hrs...
  so 3 * 3/20 + 3 * 2/15 = 9/20 + 6/15 = > 27 + 24/60 = 51/60 = 17/20
  
  Remaing tank yet to be filled = 1-17/20 = 3/20
  
  a+b ll fill d remaining 3/20 in 1 hr
  
  So total tank ll be filled in 3 + 3 + 1 = 7hrs
  
  Ans : 7 hrs
• 10 years agoHelpfull: Yes(10) No(0)
• 1st hr a+b =1/12 +1/15=9/60
  2nd hr a+c=1/12 + 1/20 =8/60
  so, 2hrs 9/60 + 8/60=17/60
  4hrs=2*17/60=34/60
  6hrs=3*17/60=51/60
  7hrs=51/60+(a+b i.,e 9/60)=60/60=1
  Therefore, it takes 7hrs....to complete...
  
  
• 9 years agoHelpfull: Yes(2) No(0)