3.51 On a river with a current speed of $5 \mathrm{km} / \mathrm{h}$, there are piers $A, B$, and $C$ in the direction of the current, with $B$ located midway between $A$ and $C$. From pier $B$, a raft and a boat depart simultaneously, with the raft moving downstream to pier $C$ and the boat heading to pier $A$. The speed of the boat in still water is $v$ km/h. Upon reaching pier $A$, the boat turns around and heads towards pier $C$. Find all values of $v$ for which the boat arrives at $C$ later than the raft.
3.51 Instruction. Take $A B=B C$ as a unit and solve the inequality $\frac{1}{v-5}+\frac{2}{v+5}>\frac{1}{5}$, where $v>5$.

Answer: $\quad 5<\nu<15$.