On a certain pasture the grass grows at an even rate. It knows that 40 cows can graze on it for 40
days before the grass is exhausted, but 30 cows can graze there as long as 60 days. How many would
the pasture last if 20 Cows were to graze on it?

• 40 cows-40 days
  30 cows-60 days
  .......
  .........
  .........
  20 cows- 80 days
• 9 years agoHelpfull: Yes(2) No(4)
• is question from this site is repeated..??
• 9 years agoHelpfull: Yes(2) No(2)
• In 40 days the pasture provides 1600 feeds and in 60 days 1800 feeds. Thus 20 days growth on the pasture allows for 200 extra feeds or, alternatively, enough grass grows everyday to feed ten cows. Consequently, the quantity of grass on the pasture before the cows start grazing is enough for (1600-40x10) or (1800-60x10) i.e. 1200 feeds. We have already seen that the daily growth is adequate to feed 10 cows endlessly. So, out of 20 cows the remaining 10 would take 120 days to consume the 1200 feeds that already exist on the pasture. Hence, the pasture would last 120 days if 20 cows were to graze on it.
• 9 years agoHelpfull: Yes(2) No(0)
• 
  
  In 40 days the pasture provides 1600 feeds and in 60 days 1800 feeds.
  Thus 20 days growth on the pasture allows for 200 extra feeds or, alternatively, enough grass grows everyday to feed ten cows.
  Consequently, the quantity of grass on the pasture before the cows start grazing is enough for (1600-40x10) or (1800-60x10) i.e. 1200 feeds.
  We have already seen that the daily growth is adequate to feed 10 cows endlessly.
  So, out of 20 cows the remaining 10 would take 120 days to consume the 1200 feeds that already exist on the pasture.
  Hence, the pasture would last 120 days if 20 cows were to graze on it.
• 9 years agoHelpfull: Yes(2) No(0)
• for 40 cows it takes 40 days to finish one work(grazing the whole pasture.)
  for 30 it takes 60 days to finish
  from the pattern, for every -10 cows the day increase by 20 more days.
  hence 30-20 cows graze in 60 +20 days i.e. 80 days.
• 9 years agoHelpfull: Yes(2) No(1)
• 40*1=40
  30*2=60
  20*3=60
• 9 years agoHelpfull: Yes(1) No(1)
• 40*40=1600
  30
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  40*40=1600
  30*60=1800
  both diff=200
  20->200
  10day
  1600-400=1200
  1800-600=1200
  then 1200/10=120day
  
  
  
  
  
  
  8
• 9 years agoHelpfull: Yes(1) No(0)
• 84
  40 cows eats in -40 days
  1 cow eats in - 1/40 days
  30 cows eats in -60 days
  1 cow eats in 1/60 days
  (30+40 cows)eats in 1/40+1/60=1/24
  1 cow eats in-1/70
  =1/70*1/24*20
  =1/84
  =84
  
• 9 years agoHelpfull: Yes(0) No(2)
• 40*40=1600
  30*60=1800
  1800-1600=200
  1800+200=2000
  20*x=2000
  x=2000/20=100
• 5 years agoHelpfull: Yes(0) No(0)