Q5) If A and B can do a piece of work in 7.5 days. If B works 1/2 of work and remaining work was completed by A, taking total time of 20 days to complete the work. If b is more efficient then B can do work in how many days?

• 10 days
  
  1/A + 1/B = 2/15 or (A+B)/AB= 2/15 ----(i)
  (1/2)/(1/A) + (1/2)/(1/B) = 20 or A/2 + B/2 = 20 or A+B= 40 ----(ii)
  Substituting A+B= 40 from (ii) in (i), we get AB= 300
  Now finding the factors of 300, whose sum is 40, we have 10 and 30
  As B is more efficient than A, B can do the work in 10 days.
• 7 years agoHelpfull: Yes(17) No(15)
• for doing 1/2 work A takes 20 days
  for doing 1 work A will take 40 days
  sp 1/40+1/B=2/15 which gives B does the work in 10 days and is more efficient as it shows
• 7 years agoHelpfull: Yes(13) No(11)
• a and b oneday work is 1/7.5
  half of the work completed by a in 20 days
  => a takes 40 days to complete the work
  a+b=1/7.5
  b oneday work =1/7.5-1/40
  b can complete the work in 9.23 days =10 days
• 6 years agoHelpfull: Yes(9) No(1)
• 10 days
  2{(1/x)+(1/(20-x))}=1/7.5
  
  so, x=10,30
  as b is more efficient, hence B can do work in 10 days.
• 7 years agoHelpfull: Yes(4) No(0)
• approx 10 days, as A will do whole work in 40 days take lcm of 40 and 15/2
  it will come out 120 now A's one day work=120/40=3 and (A+B) one day work =120*2/15=16.
  hence B's one day work=16-3=13 so, B will do whole work in 120/13=9.23 Days
• 6 years agoHelpfull: Yes(2) No(0)
• 1/a=1/b=1/7.5
  1/a+1/b=4/30
  since A is more efficient
  a can do 3/30and b=1/30
  a finishes half work so 1/2 work is left hence 1/2 by b
  that is 15 days
  B can do the work in 15 days
• 6 years agoHelpfull: Yes(0) No(5)