Nine cards with the same size and texture are marked with nine numbers from 1 to 9 respectively. What is the probability of drawing a card marked with a prime number from them?
九张大小质地相同的卡片上分别标有1～9九个数字，从中抽到一张标有素数的卡片可能性大小为多少．
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

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