There is a slope road from A to B. A car travels 30 kilometers per hour when going uphill and 40 kilometers per hour when going downhill. It takes 7 hours to go back and forth. How many kilometers is the distance between A and B?
甲地到乙地是斜坡路，一辆汽车上坡时每小时行30千米，下坡时每小时行40千米，往返一共用了7小时，则甲乙两地相距多少千米？
<gadget id="calculator">7 * 40</gadget>
<output>280</output>

<gadget id="calculator">30 + 40</gadget>
<output>70</output>

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

<gadget id="calculator">30 * 4</gadget>
<output>120</output>

<result>120</result>