A is thrice as good a workmen as B and so takes 60 days less than B for doing a job. Find the time in which they can do it together.

a)22.5 days
b)20 days
c)23.75 days
d)21.5 days

• A = (1/3)B
  B - A = 60
  B - (1/3)B = 60
  Multiply through by 3:
  3B - B = 180
  2B = 180
  B = 180/2
  B = 90
  A = (1/3) * 90
  A = 30
  
  So A can do the job in 30 days, so A can do 1/30 of the job per day.
  So B can do the job in 90 days, so B can do 1/90 of the job per day.
  Working together, they can do (1/30) + (1/90) of the job per day, which is (3/90) + (1/90) = (3 + 1) / 90 = 4/90 =
  So the job will take 90/4 days, which is 45/2 or 22.5 days
• 9 years agoHelpfull: Yes(0) No(0)
• given A is thrice workman as B
  A=B/3
  A:B=1:3
  3x-x=60
  x=30
  A takes 30 days and B takes 90 days
  A&B can do work in AB/A+B
  90*60/(90+60)=22.5 days
  
  
• 9 years agoHelpfull: Yes(0) No(0)