Answer
The width of the pool is $40$ yards, and the length is $120$ yards.
Work Step by Step
Let the width of the pool be $ w.$
We are told that the length is $3w.$
The perimeter equals 2$\times $(width + length)
=$2(w+3w)=2(4w)=8w $
Given $8w=320$
We divide with $8.$
$ w=40$
Thus, the width of the pool is $40$ yards, and the length is $120$ yards.
