A ship sails from port A to port B. It takes 3 hours along the current and 24 kilometers per hour against the current for 5 hours. Find its average speed.
轮船从A港开往B港，顺水用了3小时，逆水每小时行24千米，行了5小时，求它的平均速度．
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">24 * 5 * (1/4)</gadget>
<output>30</output>

<result>30</result>