Answer: There are 6 sheeps grazing on each acre of the pasture.
Explanation:
Hi, to answer this question we simply have to divide the number of sheep (250) by the number of acres (40). 
Mathematically speaking: 
250 sheep / 40 acres = 250/4= 6.25 sheep per acre ≅ 6 sheep 
There are 6 sheep grazing on each acre of the pasture. 
Feel free to ask for more if needed or if you did not understand something.