Plant a lawn of 100 square meters, plant 10% on the first day, and plant the rest (1/10) on the second day, how many square meters of this lawn are not planted.
种一块100平方米的草坪，第一天种了10%，第二天种了剩下的(1/10)，这块草坪还有多少平方米没种．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">100 * (1/10)</gadget>
<output>10</output>

<gadget id="calculator">100 - 10</gadget>
<output>90</output>

<gadget id="calculator">1 / 10</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">90 * (9/10)</gadget>
<output>81</output>

<result>81</result>