On a certain pasture grass grows at a even rate. It is known 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 days would pasture last if 20 cows were to graze on it ?

If initial amount of grass was X

If rate of growth of grass per day is Y

If rate of grass consumed per cow per day is Z

then Y = 10 Z

and X=1200 Z

then time taken for 20 cows would be

1200/10 = 120 days

 

Posted by salil on 2006-02-06 03:25:42