Answer :
Step 1
assume width is X
then length equals 5 X
the area of the lake 9/20 = 5X^2
So X^2 = 9/100
X = 3/10
so the width is 3/10 mile
length 3/10 * 5 = 1 1/2 mile
assume width is X
then length equals 5 X
the area of the lake 9/20 = 5X^2
So X^2 = 9/100
X = 3/10
so the width is 3/10 mile
length 3/10 * 5 = 1 1/2 mile