Answer: 700 yards of fencing (assumed).
Explanation:
To be able to calculate the number of yards that Farmer Johnson needs, you will have to know the dimensions of the field.
I will therefore assume certain figures and you can use it as a reference.
Assume that the field is a rectangular field that measures 200 yards in length and 150 yards in breath.
This means that the amount of yards needed will be the perimeter of the yard:
Perimeter = (Length * 2) + (Width * 2)
= (200 * 2) + ( 150 * 2)
= 400 + 300
= 700 yards of fencing.