The hour hand is 15 cm long, what is the distance traveled by the tip of the hand in one day and night?
时针长15厘米，一昼夜针尖端所走路程的是多少厘米．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">3.14 * 30 * 2</gadget>
<output>188.4</output>

<result>188.4</result>