A gear with a diameter of 40cm drives a gear with a diameter of 26cm (interlocking with each other). If the big gear rotates 13 times, how many times does the small gear rotate?
一个直径为40cm的齿轮带动一个直径为26cm的齿轮(相互咬合)，如果大齿轮转13圈，则小齿轮转多少圈．
<gadget id="calculator">3.14 * 40 * 13</gadget>
<output>1_632.8</output>

<gadget id="calculator">3.14 * 26</gadget>
<output>81.64</output>

<gadget id="calculator">1_632.8 / 81.64</gadget>
<output>20</output>

<result>20</result>