A car goes to the county town at a speed of 2.5 km per minute for half an hour, and returns at a speed of 120 km per hour. How many minutes does it take for the car to return? (Solve with ratio)
一辆汽车去县城以每分钟2.5km的速度，行了半小时，返回时以每小时120km的速度行驶，汽车返时用了多少分钟？(用比例解)
<gadget id="calculator">2.5 * 30</gadget>
<output>75</output>

<gadget id="calculator">120 / 60</gadget>
<output>2</output>

<gadget id="calculator">75 / 2</gadget>
<output>75/2 = around 37.5</output>

<result>75/2 = around 37.5</result>