There are plastic balls of the same size and quality in a carton, including 2 green ones, 3 yellow ones and 5 red ones. If you touch any one of them, what is the probability of getting a red ball?
纸箱里放有大小、质量完全相同的塑料球，其中2个绿的、3个黄的、5个红的．从中任意摸一个，摸出红球的可能性是多少．
<gadget id="calculator">2 + 3 + 5</gadget>
<output>10</output>

<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

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