The flying speed of the swallow is about 39 kilometers per hour. How many kilometers does it fly for (5/13) hours?
燕子的飞行速度大约是每小时39千米，飞行(5/13)小时，飞行了多少千米？
<gadget id="calculator">5 / 13</gadget>
<output>5/13 = around 0.384615</output>

<gadget id="calculator">39 * (5/13)</gadget>
<output>15</output>

<result>15</result>