From A to B, if you ride a bicycle, travel 15 kilometers per hour and arrive in 4 hours. If it takes only 2 hours by car, how many kilometers per hour will the car travel?
从甲地到乙地，如果骑自行车，每小时行15千米，4小时到达．如果乘汽车，只需2小时，汽车每小时行多少千米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>