The diameter of a wheel is 50 cm, how much m does the wheel move forward when it rotates 30 times?
一个车轮的直径为50cm，车轮转动30周，前进多少m．
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3.14 * (1/2) * 30</gadget>
<output>47.1</output>

<result>47.1</result>