A and B working separately, can do a piece of work in 12 and 15 days. They work on alternate days starting with A on the first day. In how many days will the work be completed?

• alternatively (A+B)'s consecutive two day's work=1/12+1/15=3/20
  after 12 days
  3/20*6=18/20
  work remaining 2/20
  at 13th day 2/20-1/12=1/60(work remaining)
  at 14th day 1/60*15=1/4
  it takes 1/4 of 14th day
  so total 13 and 1/4days
• 13 years agoHelpfull: Yes(11) No(4)
• work completed in 12 days = (1/12 +1/15)*6 = 6*3/20 = 18/20 work = 9/10 work
  work done by A on 13 th day = 1/12
  work left after 13 days = 1- 9/10 -1/12 = 1/10-1/12 = 1/60
  1/60 work will be completed by B on 14 th day by taking quarter of a day.
  
  so total 13 1/4 days.
• 13 years agoHelpfull: Yes(5) No(4)
• One day work of A = 1/12
  One day work of B = 1/15
  A work on first day and B work on second day then A+B will be their two day work
  A+B = 1/12+1/15 = 3/20 (this is two day work)
  if 3/20 work -------> 2 day work then
  1 work ---------> x days
  > x(3/20) = 2
  > x = 2*(20/3)
  > x = 40/3
  > x = 13 1/3 or 13.333
• 3 years agoHelpfull: Yes(0) No(0)