It takes 2.1 hours to go from A to B by car. If you ride a bicycle, you can travel an average of 10.5 kilometers per hour, which is 2.9 hours longer than by car. How many kilometers per hour are you traveling by car on average?
从甲地到乙地如果乘车要用2.1小时，如果骑自行车，平均每小时行10.5千米，比乘车多花2.9小时，乘车平均每小时行多少千米？
<gadget id="calculator">2.1 + 2.9</gadget>
<output>5</output>

<gadget id="calculator">5 / 2.1</gadget>
<output>2.380952</output>

<gadget id="calculator">10.5 * 2.380952</gadget>
<output>24.999996</output>

<result>24.999996</result>