The distance between A and B is 350 kilometers. It takes 4 hours for a car to travel from A to B, and it takes 1 hour less to return. What is the average speed of this car going back and forth?
A、B两地相距350千米，一辆汽车从A地行驶到B地用了4小时，返回时少用1小时，这辆汽车往返的平均速度是多少．
<gadget id="calculator">350 * 2</gadget>
<output>700</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">700 / 7</gadget>
<output>100</output>

<result>100</result>