The natural numbers from 1 to 20 are written on 20 cards, and each card is turned upside down on the table. If one is drawn at random, what is the probability of drawing a prime number?
在20张卡片上写着1～20的自然数，每张卡片反扣在桌面上，任意抽一张，抽到质数的可能性是多少．
<gadget id="calculator">8 / 20</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>