Ans: (a) $31$ minutes (b) $7.8\text{ km}$ (c) Billy runs faster.
- Billy rests from 1:32 p.m. to 2:03 p.m. Therefore he rests for $31$ minutes.
- The average speed of Ada
$\begin{array}{cl}
= & \dfrac{12-0}{2} \\
= & 6 \mbox{ km/h}
\end{array}$Note that they will meet at 2:18 p.m. Therefore, the required distance
$\begin{array}{cl}
= & 6 \times \dfrac{78}{60} \\
= & 7.8 \mbox{ km}
\end{array}$ - The average speed of Billy
$\begin{array}{cl}
= & \dfrac{16-2}{2} \\
= & 7 \mbox{ km/h} \\
\end{array}$Therefore, Billy runs faster.
