A &B working separately can do a piece of work in 9 & 12 days respectively. If they work for a day alternatively, A beginning, in how many days, the work will be completed?

• (A+B)'s 2 days work = (1/9 + 1/12)= 7/36
  (A+B)'s 10 days work = 10/2 *7/36 = 35/36
  remaining work (1- 35/36 = 1/36) has to be done by A on 11th day,
  its done by A in 9* 1/36 = 1/4 day
  
  total time = 10 +1/4 = 41/4 days
  
• 10 years agoHelpfull: Yes(34) No(4)
• A can do 1/9 work in 1 day
  B can do 1/12 work in 1 day
  after first two days 1/9+1/12= 7/36 work will be done.
  after each working 5 days..total work will be done = 35/36
  dat means total days of work = 2*5 = 10
  
  work remains 1/36 which is less than 1/9 so at the 11th day A will get the job done.
  I hope this one was easy to understand, any doubt please let me know.
• 10 years agoHelpfull: Yes(15) No(2)
• (A+B)'s 2 days work = (1/9 + 1/12)= 7/36
  (A+B)'s 10 days work = 10 *7/36 = 35/36
  remaining work (1- 35/36 = 1/36) has to be done by A on 11th day,
  its done by A in 9* 1/36 = 1/4 day
  
  total time = 10 +1/4 = 41/4 days
• 10 years agoHelpfull: Yes(5) No(9)
• ans:10(1/4)
  a=9 b=12 total works=36 per day work for a=4,b=3
  a start.4,3,4,3...=10(1/4)
• 9 years agoHelpfull: Yes(5) No(0)
• i can solve this by shortcut method....
  A=9,B=12 than take lcm of these numbers is 36 units.
  now
  A=36/9=4 units/day
  B=36/12=3 units /day
  now
  day work
  A(1st day) 4 units/day
  B(2nd day) 3 units/day
  --------- -----------
  so day=2 work=7 units/day
  
  now go nearest to lcm number 36 by the help of 7
  so 7*5=35
  
  so
  day work
  2*7=14 7*5=35 units/day
  
  so 1 units is remaining because total unit is 36 -35=1
  now the turn of A ..A work 4 units/day
  means 4 units--------1day
  we need only 1 unit from A
  so 4 units-------1 day
  1 unit--------1/4 day
  so answer is
  1
  14 -----=57/4 day ......ans
  4
• 9 years agoHelpfull: Yes(5) No(6)
• work to be done by both= 36 units
  A's one day work=1/9
  B's one day work=1/12
  since they work on alternate days first day A=4 units
  second day B=3 units
  
  2 days work =7 units
  x days work =36 units
  
  2*36=7*x
  total time= 72/7 days
  
  
• 9 years agoHelpfull: Yes(4) No(3)
• plz explain how come 35/36
• 10 years agoHelpfull: Yes(2) No(0)
• 11 days.
  % work a can do in a day=11.11
  % work b can do in a day=8.33
  total work of and b=19.4%
  if they work in alternate days then in 2 days they will complte 19.44 %.
  so in 10 days(5 day each) they will complete 97% and so on 11th day work will be completed.
• 10 years agoHelpfull: Yes(1) No(0)
• (A+B)'s 1 days work = (1/9 + 1/12)= 7/36
  (A+B)'s 10 days work = 10/2 *7/36 = 35/36
  remaining work (1- 35/36 = 1/36) has to be done by A on 11th day,
  its done by A in 9* 1/36 = 1/4 day
  
  total time = 10 +1/4 = 41/4 days
• 9 years agoHelpfull: Yes(1) No(0)
• LCM of 9,12 is 36 units.(total units of work).
  A 9 days =36/9 =4 units/day.
  B 12 days=36/12=3 units/day. =>4+3=7 units for 2 days
  7*5=35 units for 2*5=10 days.
  A can do 4 units/day but we have only 1 unit remaining so he can do it 1 unit in 1/4 day..so total is 10*(1/4) days =41/4 days
  
  
  
• 9 years agoHelpfull: Yes(1) No(0)
• (A+B)'s 2days work=(1/9)+(1/7)=(7/36)
  The work done by A&B during 5pairs of days=5*(7/36)=35/36
  therefore remaining work=1-(35/36)
  on 11nth day it is A's turn
  now 1/9th pf work is done by A in 1day
  1/36 work will be done by A in 9*(1/36)=1/4days
  total time taken =1/4days
• 10 years agoHelpfull: Yes(0) No(0)
• A can do a piece of work = 9days B can do a piece of work = 12days
  1day work of A =1/9 1 day work of B = 1/12
  A+B 1 day work = 1/9+1/12 = 7/36
  2 day work of A & a+b =1/9+7/36=11/36
  11/36 work done in 2 days
  so whole work complete in (2*36/11)=6 and half days (approx)
  
• 10 years agoHelpfull: Yes(0) No(1)
• Total work =36 unit
  A work=4 unit
  B
• 6 years agoHelpfull: Yes(0) No(3)
• (A+B)'s 2 days work = (1/9 + 1/12)= 7/36
  (A+B)'s 10 days work = 10 *7/36 = 35/36
  remaining work (1- 35/36 = 1/36) has to be done by A on 11th day,
  its done by A in 9* 1/36 = 1/4 day
  
  total time = 10 +1/4 = 41/4 days
• 5 years agoHelpfull: Yes(0) No(0)