A road roller has a roller diameter of 1 meter and a length of 1.2 meters. The roller rolls 15 times per minute. How many meters does this roller advance on average per minute?
一台压路机，滚筒直径1米，长1.2米，压路机每分钟滚动15周．这台压路机平均每分钟前进多少米．
<gadget id="calculator">3.14 * 1 * 15</gadget>
<output>47.1</output>

<result>47.1</result>