Andrea has finished the third day of a six-day canoe trip. If she has completed $\frac{3}{7}$ of the trip's total distance of $168 \mathrm{~km}$, how many km per day must she average for the remainder of her trip?
(A) 29
(B) 24
(C) 27
(D) 32
(E) 26
Since Andrea has completed $\frac{3}{7}$ of the total $168 \mathrm{~km}$, then she has completed $\frac{3}{7} \times 168 \mathrm{~km}$ or $3 \times 24=72 \mathrm{~km}$.

This means that she has $168-72=96 \mathrm{~km}$ remaining.

To complete the $96 \mathrm{~km}$ in her 3 remaining days, she must average $\frac{96}{3}=32 \mathrm{~km}$ per day.

ANSWER: (D)