There are 6 red balls and 3 yellow balls in a pocket, which are identical except for their colour. Now draw a ball from it, what is the probability that it is a red ball?
口袋里有6个红球和3个黄球，它们除颜色外完全相同．现在从中摸出1个球，是红色球的可能性是多少．
<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">6 / 9</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>