Sixty men can build a wall in 40 days, but though they begin the work together, 5 men quit every ten days. The time needed to build the wall is

• 60 men can build a wall in 40 days
  Fraction of work done by 1 men in 1 day =1/(60*40) = 1/2400
  In 1st 10 days fraction of work done
  = 1/2400*10*60 = 1/4 =12/48
  Next 10 days fraction of work done
  = 1/2400*10*55 = 11/48
  Next 10 days fraction of work done
  = 1/2400*10*50 = 5/24 =10/48
  Next 10 days fraction of work done
  = 1/2400*10*45 = 3/16 =9/48
  
  In 40 days fraction of work done
  = (12+11+10+9)/48 = 42/48
  
  Remaining fraction of work = 6/48 = 1/8
  if x is the no of days to complete 1/8 work with 40 men, then
  1/2400*x*40 = 1/8
  x = 15/2
  total no of days required = 10+10+10+10+15/2
  =47 1/2days
  
• 10 years agoHelpfull: Yes(12) No(1)
• 60 men can build a wall in 40 days.
  1 men will build a wall in 40*60= 2400 days.
  In starting 10 days, work done by 60 men so total work done in 10 days is 60*10/2400= 1/4.
  Now, remaining work is 1-1/4=3/4.
  Next 10 days, work done by 55 men. So total work done is 55*10/2400=11/45.
  Now remaining work is 3/4-11/45= 91/180.
  Next 10 days, work done by 50 men. So total work done is 50*10/2400=5/24.
  Now remaining work is 91/180-5/24=107/360.
  Next 10 days, work done by 45 men. So total work done is 45*10/2400=45/240.
  Now remaining work is 107/360-45/240=79/720.
  Now, men remains 40 and work remain 79/720.
  Now, Let remaining work is done in x days.
  So, 40*x/2400= 79/720.
  On solving, x=79/12=> 6*(7/12).
  Thus total days is 10+10+10+10+6*(7/12)= 46*(7/12)
• 10 years agoHelpfull: Yes(3) No(2)
• work done by 1 men in 1 day 1/60*40= 1/2400
  
  loss of work per ten days 1/2400*-5*10 = -1/48
  
  work done in first 10 days= 1/2400*60*10 = 1/4 or( 1/4*12)=12/48
  
  next 30 days fraction of work done = (12/48 - 1/48)+(12/48- 2/48)+(12/48-3/48)
  =11+10+9/48
  total work done in 40 days =12+11+10+9/48 = 42/48
  
  Remaining fraction of work = 6/48 = 1/8
  if x is the no of days to complete 1/8 work with 40 men, then
  1/2400*x*40 = 1/8
  x = 15/2
  total no of days required = 10+10+10+10+15/2
  =47 1/2days
• 7 years agoHelpfull: Yes(0) No(0)