## Task 7 - V00707

Mr. A is driving his car on the highway at $100 \mathrm{~km} \cdot \mathrm{h}^{-1}$ past a gas station ($T_{1}$). 35 $\mathrm{km}$ behind $T_{1}$, Mr. A has to switch the fuel gauge to reserve.

Since the next gas station ($T_{2}$) on the highway is another $35 \mathrm{~km}$ away, Mr. A slows down to $60 \mathrm{~km} \cdot \mathrm{h}^{-1}$ to consume less fuel.

At what average speed will Mr. A cover the distance between $T_{1}$ and $T_{2}$ under these conditions?
For the distance of $35 \mathrm{~km}$ from $T_{1}$ to the switch to reserve, $t_{1}=\frac{s}{v}=\frac{35 \mathrm{~km}}{100 \frac{\mathrm{km}}{\mathrm{h}}}=21 \mathrm{~min}$ is required. For the second distance of $35 \mathrm{~km}$, accordingly, $t_{2}=\frac{s}{v}=\frac{35 \mathrm{~km}}{60 \frac{\mathrm{km}}{\mathrm{h}}}=35 \mathrm{~min}$.

From the total driving time of 56 minutes between $T_{1}$ and $T_{2}$, an average speed of $v=\frac{70 \mathrm{~km}}{56 \mathrm{~min}}=75 \frac{\mathrm{km}}{\mathrm{h}}$ results.