Jitka hiked a trail. After hiking $60 \%$ of the length of the trail, she had $8 \mathrm{~km}$ left to go. What is the length of the trail?
(A) $28 \mathrm{~km}$
(B) $12.8 \mathrm{~km}$
(C) $11.2 \mathrm{~km}$
(D) $13 \frac{1}{3} \mathrm{~km}$
(E) $20 \mathrm{~km}$
After Jitka hiked $60 \%$ of the trail, $100 \%-60 \%=40 \%$ of the trail was left.

From the given information, $40 \%$ of the length of the trail corresponds to $8 \mathrm{~km}$.

This means that $10 \%$ of the trail corresponds to one-quarter of $8 \mathrm{~km}$, or $2 \mathrm{~km}$.

Since $10 \%$ of the trail has length $2 \mathrm{~km}$, then the total length of the trail is $10 \cdot 2=20 \mathrm{~km}$.

ANSWER: (E)