Given 9 pieces of paper of the same size marked with numbers from 1 to 9, what is the probability of drawing a piece of paper with a prime number from them?
标有1～9数字的相同大小的纸片9张，从中抽到一张素数纸片的可能性大小为多少．
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<result>4/9 = around 0.444444</result>