The dimensions of lake are length 1.5 miles and width 0.3 miles
Solution:
Given that,
Artificial lake is in the shape of a rectangle
Let the length of lake be "a"
The width of the lake is 1/5 the length of the lake

The area of lake is 9/20 square miles
The area of rectangle is given by formula:

Substituting the values we get,

Thus, we get

Thus the dimensions of lake are length 1.5 miles and width 0.3 miles