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 130 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130km的速度行驶，汽车返回时用了多少分钟？(用比例解)
<gadget id="calculator">2.5 * 30</gadget>
<output>75</output>

<gadget id="calculator">130 / 60</gadget>
<output>13/6 = around 2.166667</output>

<gadget id="calculator">75 / (13/6)</gadget>
<output>450/13 = around 34.615385</output>

<result>450/13 = around 34.615385</result>