SOLUTION: in a grass field, If there are 40 cows, they could eat for 40 days. If there are 30 cows, they could eat for 60 days. Than if 20 cows, How much day they could eat?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: in a grass field, If there are 40 cows, they could eat for 40 days. If there are 30 cows, they could eat for 60 days. Than if 20 cows, How much day they could eat?      Log On


   

Question 2036: in a grass field, If there are 40 cows, they could eat for 40
days. If there are 30 cows, they could eat for 60 days. Than if 20
cows, How much day they could eat?
Answer by Jessmh123(22) About Me  (Show Source):
You can put this solution on YOUR website!
I am not sure of my solution - but this is how i did it:
Assume that the rate at which the grass is eaten is partly dependent on the number of cows.
Then,
nDays = k1 * nCows + k2
thus,
40 = 40k1 + k2
60 = 30k1 + k2
Solving for k1, k2;
k1 = -2, k2 = 120
Therefore,
in case of 20 cows:
nDays = 20*-2 + 120 = 80 days
:) I hope I helped!