If A is 20% less efficient than B. If B alone can do the work in 40 days. In how many days can A and B together complete the same work ?

(a) 22 2/9
(b) 20 1/9
(c) 21 2/9
(d) 32 2/9

• B does 1/40 work in 1 day.
  So, A will do 80% of 1/40 work, i.e., 1/50 work in 1 day.
  Both together do (1/40 + 1/50 ), i.e., 9/200 work in 1 day.
  So, time taken to complete work together will be 200/9 days, i.e., 22 2/9 days.
  
  Option(a)
• 9 years agoHelpfull: Yes(6) No(0)
• Ratio of efficiency=80:100
  ratio of times taken by A and B=100:80=5:4
  A alone takes x days to do the job.
  then,5:4::x:40
  4x=40*5
  x=50
  A alone takes 50 days
  1 day work when A and B works together =(1/50)*(1/46)
  =9/200
  A and B together complete the same work in 200/9 days=22 2/9 days
• 9 years agoHelpfull: Yes(2) No(0)
• Ratio of time taken by A and B=120:100=6:5
  Suppose A alone takes x days to do the job.
  Then, 6:5::x:40 =>5x=6*40 =>x=48 days
  (A+B)'s 1 day's work=1/48+1/40=11/240
  A and B together complete the work in =240/11=21 9/11 days
• 9 years agoHelpfull: Yes(1) No(4)
• suppose B is 100% efficient ,then A is 80%efficient
  ratio of efficiencies of A and B is 80:100=4:5
  ratio of times to complete work=5:4
  B takes 40 days ,so 5:4=x:40(assuming A can do in x days)
  =>200=4x
  =>x=50
  Now they together can complete the work in (1/50)+(1/40) =200/9 days
• 9 years agoHelpfull: Yes(0) No(0)
• Let us Suppose Efficiency of B is 100 then A is 80.
  So Efficiency of A+B = 180
  Work to be done A and b = 100 * 40 = 4000
  Days to complete work by Both A + B = 4000 / 180 = 22 2/9 (a option )
• 4 years agoHelpfull: Yes(0) No(0)