A passenger ship travels from port A to port B at a speed of 35 km/h and takes 24 hours. When returning, the speed is 42 km/h, how long did it take to return?
一艘客轮从甲港到乙港，去的时候速度是35千米/时，用了24小时．返回的时候速度是42千米/时，返回时用了多久时间？
<gadget id="calculator">24 / 42</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">35 * (4/7)</gadget>
<output>20</output>

<result>20</result>