Ans: (a) $30\text{ km}$ (b) $8:36$ am (c) No
- The speed of car $A$
$\begin{array}{cl}
= & \dfrac{80}{2} \\
= & 40 \text{ km/h}
\end{array}$Hence, at $8:15$ in the morning, the distance of car $A$ from town $X$
$\begin{array}{cl}
= & 40 \times \dfrac{45}{60} \\
= & 30 \text{ km}
\end{array}$ - Note from the graph, car $A$ and car $B$ first meet at the distance $44\text{ km}$ from town $X$. Hence, the required time
$\begin{array}{cl}
= & 44 \div 40 \\
= & 1.1 \text{ hours} \\
= & 66 \text{ minutes}
\end{array}$Therefore, they meet at $8:36$ in the morning.
- Since car $A$ travels at constant speed during the whole period, then the average speed of car $A$ during the period $8:15$ to $9:30$ is $40\text{ km/h}$. The average speed of car $B$ during the period $8:15$ to $9:30$
$\begin{array}{cl}
= & \dfrac{80-44}{1.25} \\
= & 28.8 \text{ km/h}
\end{array}$which is slower than that of car $A$. Therefore, I don’t agree.
