There used to be 4 billion species of living things on the earth, but now there are only about 50 million species left. How many percent of the living things have become extinct?
地球上曾经生活着40亿种生物，现在只剩下5000万种左右，这表明有百分之几的生物已经灭绝？
<gadget id="calculator">40 - 0.5</gadget>
<output>39.5</output>

<gadget id="calculator">39.5 / 40</gadget>
<output>0.9875</output>

<result>0.9875</result>