A and B completed a work together in 5 days. Had A worked at twice the speed and B at half the speed, it would have taken them four days to complete the job. How much time would it take for A alone to do the work?

• a nd b's 1 day work, a+b=1/5
  with twice d speed of a nd half of b completes work in 4 days,
  so, 2a+b/2=1/4.
  on solving both d eq. we get a=1/10
  so a will complete d whole work in 10 days.
• 10 years agoHelpfull: Yes(95) No(6)
• let speed of a and b are x and y.so let total work is A.so now x=y=A/5
  A=5x+5y
  next a speed double b speed half so 2x+y/2=A/4
  8x+2y=A
  so 8x+2y=5x+5y
  3x=3y
  x=y
  so 2x of speed will complete work in 5 days
  then x speed will complete in 10 days
• 10 years agoHelpfull: Yes(9) No(1)
• Ans will be 10 days..
• 10 years agoHelpfull: Yes(8) No(8)
• a and b 's 1 day work, a+b=1/5
  with twice speed of a and half of b completes work in 4 days ,1 day work now 2a+b/2=1/4
  on solving both eqatns get a=1/10(work),wich means 10 days.
• 10 years agoHelpfull: Yes(5) No(1)
• let a & b be their efficiency .
  then 1/a + 1/b = 1/5
  now a's gets doubled and b's gets half .. their new efficiency be a'=2a , b' = b/2
  then 1/a' + 1/b' = 1/4 (i.e) 1/2a + 2/b = 1/4
  on solving these two eq we get a = 30/7
• 10 years agoHelpfull: Yes(4) No(4)
• 
  a nd b's 1 day work, 1/a+1/b=1/5
  with twice d speed of a nd half of b completes work in 4 days,
  so, 2/a+1/2b=1/4.
  
  so solving eqs we got a=10
  
  
• 8 years agoHelpfull: Yes(4) No(3)
• a and b 's 1 day work, a+b=1/5
  with twice speed of a and half of b completes work in 4 days ,1 day work now 2a+b/2=1/4
  on solving both eqatns get a=3/40(work),wich means 40/3 days 13+1/3
• 10 years agoHelpfull: Yes(3) No(3)
• to solve the problems on time and work always use this shortcut. It will save a lot of time and its very easy.
  M1D1T1E1/W1=M2D2T2E2/W2 (where M1=no. of men D1=DAYS T=TIME E1=EFFICENCY) THIS Formula can be changed according to our need. Suppose if we have no. of men and no. of days todo work given and we have to find out how many days n men will take then the equation will change to M1D1=M2D2 .
  IN the above question we have no. of days and efficiency given let the initial efficiency of both A and B is 100 then
  M1E1=M2E2
  5*200=A*100=10
  OR
  4*250=A*100=10 (IN THIS CASE A WORKS WITH DOUBLE EFFICIENCY AND B WITH HALF)
• 8 years agoHelpfull: Yes(3) No(0)
• in 1 hour work done by A+B is 1/5
  Given A:B=2:1
  let is A done a work in x hour then B than it at 2x hour
  so, in 1 hours work done by alone A=1/x
  and in 1 hour work done by alone B=1/2X
  SO 1/x+1/2x =1/5 after sovle it x=7.5
  than A than that work in 7.5 hours and B done it 15 hours
• 10 years agoHelpfull: Yes(2) No(7)
• a nd b's 1 day work, a+b=1/5
  with twice d speed of a nd half of b completes work in 4 days,
  so, a/2+2b=1/4.
  on solving both d eq. we get a=1/10
  so a will complete d whole work in 10 days.
• 7 years agoHelpfull: Yes(1) No(2)
• A work a twice then b and bhalf of the speep then, 2A+B/2= 1/4
  AND A+B=1/5 then solve the eq. we get, A+B=1/10 THEN AMS. 10DAYS
• 10 years agoHelpfull: Yes(0) No(0)
• [VIKAS SINGH]
  a nd b's 1 day work, a+b=1/5
  with twice d speed of a nd half of b completes work in 4 days,
  so, 2a+b/2=1/4.
  on solving both d eq. we get a=1/10
  so a will complete d whole work in 10 days.
• 10 years agoHelpfull: Yes(0) No(2)