A and B can finish a piece of work in 20 days .B and C in 30 days and C and A in 40 days. In how many days will A alone finish the job
(a) 48
(b) 34 2/7
(c) 44
(d) 48

• A and B can finish a piece of work in 20 days .B and C in 30 days and C and A in 40 days.
  2*(A+B+C)'s one day work = 1/20 + 1/30 +1/40 = 13/120 work
  (A+B+C)'s one day work = 13/240 work
  A's one day work = 13/240 - 1/30 = 5/240 = 1/48
  
  so A alone can complete work in 48 days.
• 12 years agoHelpfull: Yes(5) No(2)
• 1/a+1/b=1/20......(1)
  1/b+1/c=1/30.......(2)
  1/c+1/a=1/40...(3)
  Adding (1) and (3) and subtracting (2) we get 2*(1/a)=5/120
  so 1/a=5/240
  so a=48 days
• 12 years agoHelpfull: Yes(3) No(2)
• Ans 48 days
  (A+B) 1 day=1/20 ,(B+C) 1 day=1/30, (C+A) 1 day=1/40
  (A+B)-(B+C)=(A-C)=1/20 - 1/30=1/60
  Now (A-C)+(C+A)=2A=1/60 +1/40= 1/24
  Therefore A's 1 day work=1/(2*24)=1/48
  So A can complete the work in 1/(1/48)=48 days
• 12 years agoHelpfull: Yes(2) No(1)
• ( A+B )+(B+C)+(C+A) = (1/20) + (1/30) + (1/40)
  
  2(A+B+C) = 13/120
  
  (A+B+C) = (13/240)
  A's work is
  
  (A+B+C) - (B+C) = (13/240) - (1/30) = 1/48
  
  
  SO 48 days...
• 9 years agoHelpfull: Yes(1) No(0)
• ans is 48
  gn:
  per day work of each
  A+B=1/20
  B+C=1/30
  A+C=1/40
  by solving above 3 eqns
  we get
  A=5/240
  =>In days we consider 240/5=48
• 12 years agoHelpfull: Yes(0) No(0)
• a+b 1 day work is 1/20,b+c=1/30,(c+a)=1/40
  2(a+b+c) 1 day work is 1/20+1/30+1/40
  so a+b+c 1 day work is 13/240
  a 1 day work is (a+b+c)-(b+c)=13/240-1/30
  1/48
  so a can finish in 48 days
• 12 years agoHelpfull: Yes(0) No(0)
• Let 120 unit be the total work.Then in one day,
  A+B=6 unit
  B+c=4 unit
  A+C=3 unit
  Solving this ...We get,
  A=2.5 unit in 1 day
  Hence 120 unit in 48 days.
• 7 years agoHelpfull: Yes(0) No(0)
• A+B=20 days
  B+C=30 days
  C+A=40 days
  Take out LCM of above three i.e., LCM of 20,30and 40 which will be 120(and this will be total work).
  Therefore, A+B= 6 work/day....(1)
  B+C= 4 work/day....(2)
  C+A= 3 work/day....(3)
  Adding all of the above three equations we get A+B+C= 13/2....(4)
  From equation 2 and 4, we get A=5/2.
  Therefore eff.=work/time
  120*2/5=48 days
• 5 years agoHelpfull: Yes(0) No(0)