Given 20 balls, 3 white balls, 4 yellow balls, and 3 red balls, what is the probability of getting a yellow ball?
20个球，其中3个白球，4个黄球，3个红球，摸到黄球的可能性是多少．
<gadget id="calculator">4 / 20</gadget>
<output>1/5 = around 0.2</output>

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