1) We know the equation to find area is A=lw. Because we want to find the length, we need to get l alone. In order to do this, we must divide w on both sides to get A/w=l.
2) Now we can insert the information we know into this equation to get 5 1/5 / 1 19/20 = l.
3) To make this division easy, turn the proper fractions into improper fractions: 26/5 / 39/20 = l
4) To divide two fractions, flip the denominator and multiply it by the numerator: 26/5 * 20/39 = 8/3.
5) 8/3 = l
Answer
The park is 8/3 miles.