8. The shortest path from Atown to Cetown runs through Betown. The two signposts shown are set up at different places along this path. What distance is written on the broken sign?
A $1 \mathrm{~km}$
B $3 \mathrm{~km}$
C $4 \mathrm{~km}$
D $5 \mathrm{~km}$
E $9 \mathrm{~km}$
Solution
A

The information on the signs pointing to Atown and the signs pointing to Cetown both tell us that the distance between the signs is $(7-2) \mathrm{km}=(9-4) \mathrm{km}=5 \mathrm{~km}$. Therefore the distance which is written on the broken sign is $(5-4) \mathrm{km}=1 \mathrm{~km}$.