g and s working seperately can mow a field in 8 and 12 hours.if they work in stretches of 1 hour alternately,ganga begining at 9 am,when will they complete?

• Altogeather in 2 hours they do 1/8 +1/12= 5/24
  in 8 hours 20/24 wok get completed
  in 9th hour ganga again comes do 20/24+1/8 = 23/24 work get completed in 9 hours
  1/24 work left , s comes
  s do 1/12 in 1 hour
  for 1/24 it takes 0.5 hour
  so total time 9.5 hours
  so 6.30 pm ans ?
  
  
  
  6.30 pm
• 7 years agoHelpfull: Yes(12) No(0)
• Work done by them in 2 hour =1/8+1/12=5/24
  Work completed by them in 8 hours=4*(5/24)=20/24
  Work left=1-(20/24)=4/24=1/6
  Now A will complete 1/8 part of work in next 1 hour
  work left=1/6-1/8=1/24
  now B can complete 1/24 of work in 1*12*(1/24)=1/2 hours
  so total time=9 hours 30 minutes
  work will finish at 6:30
• 7 years agoHelpfull: Yes(3) No(0)
• For these questions follow the below mentioned simple trick, I have explained so it might look lengthy but you have to do these calculation orally so it wont take even a minute.
  
  G's work- 8
  S's work- 12
  Take LCM of 8 & 12 = 24 (Total work)
  Now, time taken by G to do 1 work = 24/8=3
  time taken by S to do 1 work =24/12=2
  G starts @ 9 am so she does her 1 work which is equivalent to 3.
  Remaining = 24-3 = 21
  Next comes S and does 1 work which is equivalent to 2.
  Remaining = 21-2=19....
  This way they work for 4 times each.. Work done= (3+2)*4 = 20.
  Remaining work =24-20=4
  Now G does 1 work So remaining work = 1
  S will do the remaining work in 30 minutes as half of the work is left.
  
  Total time = 9am +(9hrs+30mins)
  =18:30hours or 6 :30pm.
• 7 years agoHelpfull: Yes(3) No(0)
• g is ganga and s is someone else.
  
  Now suppose the total work to be finished is = LCM(8,12)=24
  
  We know, Efficiency= work/time
  
  therefore, efficiency of G = 24/8=3
  (which means G can do 3 amount of work in 1 hour)
  
  and Efficicnecy of S= 24/12=2
  (which means S can do 2 amount of work in 1 hour)
  
  Now, it is given that the work is started at 9:00 am and G i.e Ganga started the work-
  
  Total work to be finished = 24
  
  G does work for 1 hour and then S does the same work for next 1 hour, i.e 5 amount of work is completed in 2 hours.
  
  Therefore- 5 amount of work is completed in every 2 hour,
  
  Total work is 24.
  
  (5W=2hour) *4
  which means 20 work will be completed in 8 hour and G will do te work in next hour i.e 3w is also done for next hour.. i.e 23w is completed in 9 hours
  
  now 1w is left and S has to complete it now-
  
  S does 2w in 1hr..
  so 1w will be done in 1/2hr
  
  so total time taken will be- 9hours 30minutes
  
  work was started at 9:00 am and will be completed after 9 hours 30 minutes later
  
  therefore answer will be:- 6:30 pm
• 7 years agoHelpfull: Yes(3) No(0)
• ans is 6:20 pm
• 7 years agoHelpfull: Yes(1) No(4)
• Take Lcm of 8 and 12 ,we get 24.In one hour g completes 24/8=3 units of work and in 1 hour s completes 24/12=2 units of work in 1 hour.In first hour g will work ,in next hour s will work,therefore in total of 2 hours 5 unit work will be done(3 units by g and 2 units by s).Therefore 20 units of work will be done in 8 hours.(20/5*2).....................................................1
  We took 20 because working alternately 20 units will be done in complete hours ,no fraction.So we have to find closest number to 24 that will be done in complete hours and that is 20.
  Remaining=4 units.Now it is G's turn ,in next 1 hour g will complete another 3 units of work..........................2
  ,now remaining is 1 unit it will be done by s in 1/2=30 mins(half hour)...................................3
  add 1,2,3=8+1+1/2=9 hours and 30 mins.therefore,6:30 pm is answer
• 5 years agoHelpfull: Yes(1) No(0)