There are 1 red ball, 2 yellow balls, 3 black balls and 4 white balls in a pocket, what is the probability that one of them is exactly yellow
口袋里有1个红球、2个黄球、3个黑球和4个白球，从中取出1个，正好是黄球的可能性是多少
<gadget id="calculator">1 + 2 + 3 + 4</gadget>
<output>10</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>