A does 4/5 of work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?

• A can do 4/5th works in 20 days.
  so he can do the whole work in 20*(5/4) =25 days.
  remaining work after done 4/5 by A is=1-(4/5)=1/5
  (A+B) can do the 1/5th work in 3 days.
  means the can do the whole work in (3*5)=15 days.
  so,(A+B)'s 1 days work=1/15
  B's 1 day's work {(1/15)-(1/25)}=2/75
  so B can alone do the whole work in 75/2,means in 37 1/2 days.
• 10 years agoHelpfull: Yes(9) No(0)
• A can do 4/5th works in 20 days.
  so he can do the whole work in 20*(5/4) =25 days.
  remaining work after done 4/5 by A is=1-(4/5)=1/5
  (A+B) can do the 1/5th work in 3 days.
  means (A+B) can do the whole work in (3*5)=15 days.
  so,(A+B)'s 1 days work=1/15
  B's 1 day's work {(1/15)-(1/25)}=2/75
  so B can alone do the whole work in 75/2,means in 37 1/2 days.
• 10 years agoHelpfull: Yes(1) No(1)
• For simplification, let the work be 60units(LCM of 20 and 3)
  A does 4/5 th work(48units) in 20 days
  Thus, A's one day work is 48/20=2.4 units
  Now A and B together can completed the remaining work in 3 days(Balance 12 units)
  In one day, A completes 2.4 units and he must have completed 2.4*3=7.2 units
  The balance 12.8 units has completed by B in 3days
  For 12.8 units, B takes 3 days
  For 60 Units , B takes 3/12.8*60=14.0625 days
• 11 years agoHelpfull: Yes(0) No(6)
• A does 4/5th work ( 48 units ) in 20 days
  Thus, A's one day work is 48/20=2.4 units
  Now A and B together can completed the remaining work in 3 days(Balance 12 units)
  In one day, A completes 2.4 units and he must have completed 2.4*3=7.2 units
  The balance (12-7.2=4.8) units has completed by B in 3 days
  For 4.8 units, B takes 3 days
  For 60 Units , B takes 3/4.8*60=37+1/2 days
• 6 years agoHelpfull: Yes(0) No(0)