A car drives from A to B at 50 kilometers per hour, and it takes 3 hours to arrive. When returning, it takes only 2 hours to return. Find the round-trip speed of this car.
一辆汽车从甲地开往乙地，每小时行50千米，3小时可以到达，返回时由于赶时间只用了2小时，求这辆汽车的往返速度．
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">50 * 3 * (2/5)</gadget>
<output>60</output>

<result>60</result>