A car drives from place A to place B, travels an average of 70 kilometers per hour, reaches place B in 9 hours, and only takes 7 hours to return. How many kilometers per hour does the car travel on average when returning?
一辆汽车从甲地开往乙地，平均每小时行70千米，9小时可到达乙地，返回时只用了7小时，返回时这辆汽车平均每小时行多少千米？
<gadget id="calculator">9 / 7</gadget>
<output>9/7 = around 1.285714</output>

<gadget id="calculator">70 * (9/7)</gadget>
<output>90</output>

<result>90</result>