After 20% of the 10-meter-long steel pipe is used up, and the remaining 20% is used up, how many meters are left
10米长的钢管用掉了20%以后，又用掉余下的20%，还剩…多少米
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * (4/5)</gadget>
<output>16/25 = around 0.64</output>

<gadget id="calculator">10 * (16/25)</gadget>
<output>32/5 = around 6.4</output>

<result>32/5 = around 6.4</result>