The length of the two ropes originally differed by 10 meters. Now, after 10% of each is cut off, what is the difference in length between the two ropes?
两根绳子的长度原来相差10米，现各剪去10%后，两根绳子的长度相差多少米
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">30 * (9/10)</gadget>
<output>27</output>

<gadget id="calculator">20 * (9/10)</gadget>
<output>18</output>

<gadget id="calculator">27 - 18</gadget>
<output>9</output>

<result>9</result>