A& B completed a work together in 5 days. A worked at twice the speed and B at half the speed it would have taken then 4 days to complete the job. How much time would it take for A alone to do the job?
option
a) 25
b) 10
c) 20
d) 15

• here A & B's one day work is 1/5
  so A+ B= 1/5
  also it is given
  2A + B/2 =1/4
  solving this equation we get A =1/10.
  which means A alone will complete the work in 10 days
• 11 years agoHelpfull: Yes(18) No(0)
• ans 10
  5(a+b)=4(2a+ b/2)
  a=b
  1/a + 1/a =1/5
  a=10
• 11 years agoHelpfull: Yes(3) No(0)
• A&B together can do in 5 days...so...
  (1/A)+(1/B)=1/5
  now a's speed is doubled and b's speed is halved.... so...
  (1/2A)+(2/B)=1/4
  solving these two we get A=10...
  so Ans=10 days
• 11 years agoHelpfull: Yes(3) No(0)
• 10 days
  Let A can do X amount of work in a day and B Y.
  Hence, 5(X+Y)=4(2X+Y/2)
  So, X=Y
  
  Hence A or B can complete the work in 10 days
• 11 years agoHelpfull: Yes(1) No(0)
• we will have two equations:
  i.1/a + 1/b =1/5.
  ii.1/2a + 2/b=1/4.
  solving these two we will get a=10.
  so the req. no of days in which a alone can complete the work=2*a=20 days.
• 11 years agoHelpfull: Yes(0) No(3)
• a+b=1/5
  a/2=2b/4
  a=b
  2a=1/5
  a=1/10
  10 dayss...............
• 11 years agoHelpfull: Yes(0) No(0)
• b) 10
  
• 11 years agoHelpfull: Yes(0) No(0)
• (1/A+1/B)=1/5
  and let the speed be x, Therefore
  (2/B+1/2B)=1/4;
  B=1/10 and A=1/10
• 8 years agoHelpfull: Yes(0) No(0)