For a basket of apples, half of it is sold for the first time, and the first (4/5) is sold for the second time. What percentage of the remaining apples in the basket have not been sold?
一筐苹果，第一次卖出它的一半，第二次卖出的是第一次的(4/5)，还剩下这筐苹果的几分之几没有卖？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/2) * (4/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>