It took Nasrin two hours and thirty minutes to canoe the $4.5 \mathrm{~km}$ into her camp. Paddling much faster, the return trip took her $\frac{1}{3}$ of the time. What was Nasrin's mean (average) speed as she paddled to camp and back?
(A) $1.25 \mathrm{~km} / \mathrm{h}$
(B) $3.96 \mathrm{~km} / \mathrm{h}$
(C) $1.8 \mathrm{~km} / \mathrm{h}$
(D) $1.95 \mathrm{~km} / \mathrm{h}$
(E) $2.7 \mathrm{~km} / \mathrm{h}$
Nasrin's mean (average) speed is determined by dividing the total distance travelled, which is $9 \mathrm{~km}$, by the total time.

It took Nasrin 2 hours and thirty minutes, or 150 minutes, to canoe into her camp.

On the return trip, it took her $\frac{1}{3} \times 150$ minutes or 50 minutes.

Thus, the total time for Nasrin to paddle to camp and back was 200 minutes.

Converting to hours, 200 minutes is 3 hours and 20 minutes, and since 20 minutes is $\frac{20}{60}=\frac{1}{3}$ hours, it took Nasrin $3 \frac{1}{3}$ hours in total.

Thus, Nasrin's mean speed as she paddled to camp and back was $\frac{9 \mathrm{~km}}{3 \frac{1}{3} \mathrm{~h}}$ or $\frac{9 \mathrm{~km}}{\frac{10}{3} \mathrm{~h}}$, which is equal to $9 \times \frac{3}{10} \mathrm{~km} / \mathrm{h}=\frac{27}{10} \mathrm{~km} / \mathrm{h}=2.7 \mathrm{~km} / \mathrm{h}$.

ANSWER: (E)