A butterfly flies 3.9 kilometers at 0.5 hours, and a bee flies 2.4 times faster than the butterfly. How many kilometers does this bee fly per hour?
一只蝴蝶0.5时飞行3.9千米，一只蜜蜂的飞行速度是这只蝴蝶的2.4倍．这只蜜蜂每时飞行多少千米？
<gadget id="calculator">3.9 / 0.5</gadget>
<output>7.8</output>

<gadget id="calculator">7.8 * 2.4</gadget>
<output>18.72</output>

<result>18.72</result>