A can complete a project in 20 days while B can complete same project in 30 days. If A and B start working together and A leaves the work 10 days before completion of project, then in how many days the project will be completed?

• A's 1day work=1/20;
  B's 1day work=1/30;
  (A+B) 1day work=(1/20+1/30)=1/12;
  
  It is given that A leaves the work 10 days before completion of the project..
  Thus,B alone does the remaining job in 10 days.
  
  So,In 10 days ,B can do 1/3 w ..
  
  Thus,(A+B) have worked (1-1/3)=2/3 w..
  (A+B)can do 1/12 work in 1 day...
  
  They did 2/3 w in 8 days.
  
  Total days=(8+10) = 18 (Ans)
  
• 10 years agoHelpfull: Yes(75) No(14)
• A's 1 day work=1/20
  
  B's 1 day work=1/30
  
  A+B's 1 day work= 1/20+1/30 = 1/12
  
  so they ll complete d work in 12 days... but A left before 10 days... So both worked together only for days...
  
  A+b's 2 day work= 2*1/12= 1/6
  
  Remaining work=5/6
  
  Remaining work can be done by B in 5/6*30= 25 days
  
  So the project ll be completed in 2+25 = 27 days
• 10 years agoHelpfull: Yes(54) No(48)
• A's 1 day work->1/20
  B's 1 day work->1/30
  
  let the project be completed in x days
  
  for (x-10) days A & B work together
  so,(1/20+1/30)(x-10)=y
  
  wer,y->work completed in x-10 days
  
  for 10 days B works alone if z is the work done by B
  z=10(1/30)=1/3
  
  total work=y+z
  1=y+1/3
  y=2/3
  
  (1/20+1/30)(x-10)=2/3
  so,x=18 days is the ans
• 9 years agoHelpfull: Yes(15) No(0)
• Let's after 10 days B alone takes x days to complete a whole project.
  then A's working day = x-10. and
  A's 1 days Work = 1/10, B's 1 days Work = 1/30
  therefore
  A's (x-10) days work + B's x days work = 1 work
  
  so (x-10)/20 + x/30 = 1 work
  => 30x-300+20x=600
  50x=900
  x = 18 days to complete whole work.............
• 10 years agoHelpfull: Yes(12) No(3)
• 27 is wrong.
  x-10/20 + x/30 =1
  then x=18 is correct.
• 9 years agoHelpfull: Yes(10) No(1)
• ans 27days
  Together they can complete the work in
  (20*30)/(20+30)=12days
  A work for 2 days (12-10 days) and B work for x days
  2/20+x/30=1
  x=27
  
• 10 years agoHelpfull: Yes(6) No(15)
• A completes the work in 20 days
  B completes the work in 30 days
  
  L.C.M of 20 and 30 is 60, hence the total work to be done is 60 units
  
  A's efficiency = 60/20 = 3 units/day
  B's efficiency = 60/30 = 2 units/day
  
  Given A left the project before 10 days , that means B has done the project alone in the last 10 days i.e, 10*( 2 units/day ) = 20 units.
  
  Remaining work = 60 - 20 = 40 units
  
  They both completed 40units of work
  40units /(3+ 2)units/day=8
  
  Therefore the project is completed in 10+8 = 18 days
• 9 years agoHelpfull: Yes(6) No(2)
• a can complete in 20 days.
  b " " " 30 days.
  
  a+b = 1/20 + 1/30
  =1/12
  
  they can finish the work in 12 days.
  
  but a leaves before 10 days.
  
  b worked for 10 days i.e. 1/3 of the work was completed by b.
  so they finished (1-1/3) i.e. 2/3 of the work.
  so it took 12 x 2/3 = 8 days.
  total time = 10+8 =18 days
• 10 years agoHelpfull: Yes(5) No(2)
• Ans : 27 days
  A one day work is =1/20
  b one day works is=1/30
  A+B works is =1/20+1/30=>50/600==>1/12
  
  A+B can complete the work in 12 days..
  A leaves the work 10 days before
  12-10=2--->2*1/12=1/6
  Remaining work is 1-1/6=5/6
  B complete the project in 30 days=30*5/6=25days
  Already they works 2 days so =25+2=27days
  B complete the project in 27 days.......
  
  
• 9 years agoHelpfull: Yes(5) No(6)
• ans is 18
  
  27 is the wrong answer .
• 9 years agoHelpfull: Yes(4) No(1)
• x/20+x/30=1
  (30(x-10)+20x)/600=1
  50x=900
  x=18.
  answer is 18 days
• 9 years agoHelpfull: Yes(2) No(1)
• A's 1day work=1/20;
  B's 1day work=1/30;
  let they finish their work in x days so
  x(1/20 + 1/30) - 10(1/20)=1
  -> x=18 days
• 10 years agoHelpfull: Yes(1) No(1)
• The rate of A frac{1}{20} job per day;
  The rate of B frac{1}{30} job per day.
  
  Say they need t days to complete the project.
  
  According to the stem we have that B works for all t days and A works only for t-10 days, thus frac{1}{20}*(t-10)+frac{1}{30}*t=1 --> t=18days.
  
  Answer: A.
• 9 years agoHelpfull: Yes(1) No(0)
• Let tank filled in x hour then
  (x-10)/20+x/30=1
  x=18
  So project will complete in 18 days
• 9 years agoHelpfull: Yes(1) No(0)
• formula for this type of questions is
  
  D= b(n+a)/ (a+b)
  b = no of days taken by B to finish the work
  a =no of days taken by A to finish the work
  n = days before A has left the work
  substituting the values we will get
  
  D= 18 days
  
  further queries check website
  http://a4academics.com/careers-guidance-jobs/68-quantitative-aptitude/674-time-and-work-shortcuts
• 8 years agoHelpfull: Yes(1) No(0)
• Ans i....after 5days project will be complete
  One day work of A is= 1/20
  One day work of B is = 1/30
  Work complete in 10 days by A = 1/2
  Work complete in 10 days by B=1/3
  Remaining work is =1-1/2-1/3=1/6
  Time taken by B is =1/6*30=5
  
  Ans is 5Days
• 10 years agoHelpfull: Yes(0) No(14)
• (x-10)/20 +x/30=1
  x=18 ans
• 9 years agoHelpfull: Yes(0) No(0)
• 27 is the answer
  
• 9 years agoHelpfull: Yes(0) No(4)
• admin galat ans ko solved likha betha hain
  
• 9 years agoHelpfull: Yes(0) No(0)
• b filled 1/16th of tank in 3hrs
  i.e
  40
  =>1/16th=40
  =>full=640
  therefor 10,20,40,80,160,320,640
  tank can fill in 7hrs
• 9 years agoHelpfull: Yes(0) No(0)
• its 18 days
• 9 years agoHelpfull: Yes(0) No(0)
• let total days be t.
  
  -> t/20 + t-10/30 =1
  ->3t+2t-20 /60 =1
  ->t = 80/5
  ->t=16 days
• 9 years agoHelpfull: Yes(0) No(0)
• (x-10)/20 + x/30 =1
  x=18 ANS
• 9 years agoHelpfull: Yes(0) No(0)
• 10 days only B works , so work by B in 10days=10*(1/30)=1/3
  rest work=1-1/3=2/3
  together work to complete 2/3 work
  so (2/3)*((20*30)/50)=8
  so 10+8=18 days
  
• 9 years agoHelpfull: Yes(0) No(0)
• Their 1 day work=(1/20+1/30)=1/12
  10 days work = 10/12=5/6 so remaining work is 1/6
  it will be done by B alone in 1/6*30 days=5 days
  so total days to complete the project will be 10+5 =15
• 9 years agoHelpfull: Yes(0) No(0)
• 10 days working of A&B is =10(1/10+1/30)
  = 2/5
  remaining work=1-2/5
  =3/5
  B alone complete the work is=(3/5)*30
  =18days
• 9 years agoHelpfull: Yes(0) No(0)
• ans is 15
  
• 9 years agoHelpfull: Yes(0) No(1)
• x-10/20 + x/30 =1
  x = 18
• 8 years agoHelpfull: Yes(0) No(0)
• The rate of A 120 job per day;
  The rate of B 130 job per day.
  
  Say they need t days to complete the project.
  
  According to the stem we have that B works for all t days and A works only for t−10 days, thus 120∗(t−10)+130∗t=1 --> t=18days.
• 8 years agoHelpfull: Yes(0) No(0)
• 18 is the answer
  27 is wrong
  
• 8 years agoHelpfull: Yes(0) No(0)
• Answer is 18 days
• 6 years agoHelpfull: Yes(0) No(0)
• LCM of 20,30 = 60
  A's 1 day work = 3
  B's 1 day work = 2
  A+B's 1 day work = 5
  
  (A+B) * x days + B *10 days = 60
  5*x + 2*10 = 60
  5x = 40
  x = 8
  
  total days = 8+10 =18
• 6 years agoHelpfull: Yes(0) No(0)