The highway from Wuhan to Yichang is 420 kilometers long. A truck travels 60 kilometers per hour when it is full of goods, and 70 kilometers per hour when it returns empty. How much time did you save when you returned compared to when you went?
武汉到宜昌的公路长420千米，一辆货车去时装满货物每小时行60千米，返回时空车每小时70千米．返回时比去时节省了多少时？
<gadget id="calculator">420 / 60</gadget>
<output>7</output>

<gadget id="calculator">420 / 70</gadget>
<output>6</output>

<gadget id="calculator">7 - 6</gadget>
<output>1</output>

<result>1</result>