A6. A train traveled the distance between towns $A$ and $B$ in 24 hours. For half of the time, it traveled at a speed of $80 \frac{\mathrm{km}}{\mathrm{h}}$, for a third of the time at a speed of $60 \frac{\mathrm{km}}{\mathrm{h}}$, and the remaining time at a speed of $40 \frac{\mathrm{km}}{\mathrm{h}}$. What is the distance between towns $A$ and $B$?
(A) $160 \mathrm{~km}$
(B) $180 \mathrm{~km}$
(C) $800 \mathrm{~km}$
(D) $1600 \mathrm{~km}$
(E) $1800 \mathrm{~km}$
A6. In the first 12 hours, the train traveled $80 \frac{\mathrm{km}}{\mathrm{h}} \cdot 12 \mathrm{~h}=960 \mathrm{~km}$, in the next 8 hours $60 \frac{\mathrm{km}}{\mathrm{h}} \cdot 8 \mathrm{~h}=$ $480 \mathrm{~km}$, and in the last 4 hours $40 \frac{\mathrm{km}}{\mathrm{h}} \cdot 4 \mathrm{~h}=160 \mathrm{~km}$. The distance between cities $A$ and $B$ is $960 \mathrm{~km}+480 \mathrm{~km}+160 \mathrm{~km}=1600 \mathrm{~km}$.

## Section B