There are 3 red balls, 5 white balls and 7 yellow balls of the same size in a pocket, and one ball is randomly drawn from among them, what is the probability of drawing a red ball?
口袋里有大小相同的3个红球、5个白球和7个黄球，从中任意摸出1个球，摸出红球的可能性是多少．
<gadget id="calculator">3 + 5 + 7</gadget>
<output>15</output>

<gadget id="calculator">3 / 15</gadget>
<output>1/5 = around 0.2</output>

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