A tourist bus travels on the plains and mountains for 4 hours each, and finally reaches the top of the mountain. The speed of the coach on the plain is 105 km/h, and the speed on the mountain is 70 km/h. How many kilometers is the total length of this road?
一列旅游车在平原和山区各行4小时，最后到达山顶．旅游车在平原的速度是105千米/时，在山区的速度是70千米/时，这段路全长多少千米？
<gadget id="calculator">105 * 4</gadget>
<output>420</output>

<gadget id="calculator">70 * 4</gadget>
<output>280</output>

<gadget id="calculator">420 + 280</gadget>
<output>700</output>

<result>700</result>