Question 445888
First, set up an equation to find the values for the length and width.

(x)* (2x) = 39200

2x^2  = 39000
x^2  = 19,600
x = 140.
The length is 280 yd.
The width is 140 yd.

So we need a length of 280 yards parallel to the river, and we need two sections of 140 for the width of the pasture.
Total, our farmer is going to need 560 square yards of fencing.
Cleomenius.