The minute hand of the naughty alarm clock is 4 cm long. From 7:30 to 8:00, how many centimeters does the tip of the minute hand travel?
淘气的闹钟分针长4厘米，从7时30分到8时，分针针尖走过了多少厘米？
<gadget id="calculator">30 / 60</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3.14 * 4 * 2 * (1/2)</gadget>
<output>12.56</output>

<result>12.56</result>