Answer: There are 36 cows that can eaten 72 acres of grass in 126 days.
Step-by-step explanation:
Let x be the amount of grass in an acre initially.
Let y be the amount of grass grown in an acre per day.
Since we have given that
12 cows can eat 10 acres of grass in 28 days
12×28 = 10x + 10×28 y
336 = 10x + 280 y----------------------------(1)
Similarly,
21 cows can eat 30 acres of grass in 63 days.
21×63 = 30x + 30×63 y
1323 = 30x +1890 y ---------------------------(2)
So, by graphing method, we get the value of x and y
So, we have, 72 acres of grass in 126 days, we need to find the number of cows.
So, it becomes,
c×126 = 72x + 72×126 y
Hence, there are 36 cows that can eaten 72 acres of grass in 126 days.