In a grass field if 40 cow could eat for 40 days.The same grass field can feed 30 cows for 60 days.how long will it feed 20 cows?

• 80
  
  Here if number of cows decrease by 10 has increasing the number of days by 20
  
  therefore,
  40cows for 40days
  30cows for 60days
  20cows for 80days
  
  Ans: 80
  
  or you can solve by ratio
  40C : 40D --> 1:1
  30C : 60D --> 1:2
  20C : 80D --> 1:4
  
  ans:80
  
  
• 8 years agoHelpfull: Yes(16) No(6)
• 30 cow 60 days
  1 cow 60*30=180 days
  20 cow 180/20= 90 days
  
  
  
  40 cow 40 days
  1 cow 40*40=160 days
  20 cow 160/20= 80 days
  
  
  
  
  
• 8 years agoHelpfull: Yes(1) No(5)
• a : consumption of 1 cow a day
  b : growth of grass a day
  T : total amount of grass at the begining
  40*a*40 = T + 40*b ---- Equation 1)
  30*a*60 = T + 60*b
  so, b = 10*a
  let's say we are looking for x which is the how-many-days to feed 20 cows.
  20*a*x = T + x*b
• 7 years agoHelpfull: Yes(1) No(0)
• acc to ques
  field feeds 30cows for 60 days
  means feeds a cow for 2 days
  so 20*2 will be 40 days
• 7 years agoHelpfull: Yes(1) No(0)
• 40cows -- 40days-- 1:1
  30cows -- 60days-- 1:2
  20cows-- ?? days--1:3 i.e 60days
  
• 8 years agoHelpfull: Yes(0) No(9)
• can anyone give clarity about the answer?
  
• 8 years agoHelpfull: Yes(0) No(0)