The car goes back and forth between the two places, travels 50 kilometers per hour when going there, and arrives in 4.5 hours. Due to the headwind when returning, it takes 1 hour longer than when going there. What is the average speed of the car round trip?
汽车往返于两地之间，去时每小时行驶50千米，4.5小时到达，返回时由于逆风，比去时多用了1小时．汽车往返的平均速度是多少？
<gadget id="calculator">50 * 4.5 * 2</gadget>
<output>450</output>

<gadget id="calculator">4.5 + 1 + 4.5</gadget>
<output>10</output>

<gadget id="calculator">450 / 10</gadget>
<output>45</output>

<result>45</result>