There are 9 balls in an opaque box. Given 2 red balls, 3 yellow balls, and 4 white balls, if one of them is chosen at random, what is the probability that it is just a red ball?
在一个不透明的盒子里放有9个球．2个红球、3个黄球、4个白球、从中任意取出一个，正好是红球的可能性是多少．
<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<result>2/9 = around 0.222222</result>