A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day?

A. 11 days
B. 15 days
C. 10 days
D. 12 days

• A+B+C 1 day work =1/20+1/30+1/60=6/60
  on first and second day A alone do work i.e 1/20+1/20
  on third day A,B,C do together.
  so work by A with the help of B and c together =1/20+1/20+6/60=12/60=1/5
  5*3days =1/5*5=1
  so total time taken by A =15 days.
  
  i.e B is answer
• 9 years agoHelpfull: Yes(36) No(5)
• Amount of work P can do in 1 day = 1/20
  
  Amount of work Q can do in 1 day = 1/30
  
  Amount of work R can do in 1 day = 1/60
  
  P is working alone and every third day Q and R is helping him
  
  Work completed in every three days = 2 × (1/20) + (1/20 + 1/30 + 1/60) = 1/5
  
  So work completed in 15 days = 5 × 1/5 = 1
  
  Ie, the work will be done in 15 days
  
• 9 years agoHelpfull: Yes(8) No(1)
• A does 5% work each day, A+B+C combined works 10% each day.
  So in 2 days A does 10% of total work and at 3rd day A+B+C work 10% of total work.
  20% work is completed in 3 days . So total 100% work get completed in 15 days.
• 9 years agoHelpfull: Yes(4) No(0)
• first solve 2 day work done by A is 2*3=6 work
  3rd day B and C also work with A so 3rd day work = 1*6= 6 work
  now 3 day work= 6+6= 12 work
  so 60 work will be done in 15 days.
• 9 years agoHelpfull: Yes(3) No(3)
• please explain it?
  
• 9 years agoHelpfull: Yes(2) No(0)
• 15 days
  
• 9 years agoHelpfull: Yes(2) No(1)
• 1st day wrk done (1/20). 2nd day (1/20), 3rd day (1/20+1/30+1/60)=1/10 in total 3dys wrk done is (1/5)
  
  so for 1day the resultant wrk done is 1/15 so the answa is 15 days..
• 9 years agoHelpfull: Yes(2) No(0)
• b. 15 days
• 9 years agoHelpfull: Yes(1) No(1)
• 11 days is d correct answer
  
• 9 years agoHelpfull: Yes(1) No(8)
• Option B. 15 is the right answer
• 9 years agoHelpfull: Yes(1) No(1)
• Let x be the total working days.
  A=1/20.
  B & C work on every third day so total work done by B in 3 days is 1/30.
  So in one day, B=(1/30)*(1/3)=1/90. Similarly C=1/180.
  Now eq is,
  Ax+Bx+Cx=1 -> x(1/20+1/90+1/180)=1 -> x=15.
  Ans: B
• 9 years agoHelpfull: Yes(1) No(1)
• harish finishes 1/20 work in a day. together they finish1/10 work in a day. for first three days work done will be1/20+1/20+1/10=1/5 so a total of five 3 day pairs are required thus total no. of days are5*3=15
• 9 years agoHelpfull: Yes(1) No(0)