There are 3 red balls, 4 yellow balls, and 1 green ball in a pocket. If you touch any one, what is the probability of getting a yellow ball?
口袋中有3个红球，4个黄球，1个绿球，任意摸1个，摸到黄球的可能性是多少．
<gadget id="calculator">3 + 4 + 1</gadget>
<output>8</output>

<gadget id="calculator">4 / 8</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>