There are 3 red balls and 6 white balls in a box (the red balls and the white balls have the same shape and size). If you touch a ball at random, what is the probability that you get exactly the red ball?
箱子里有3个红球，6个白球(红球、白球的形状大小都一样)．从中任意摸一个球，正好摸到红球的可能性是多少
<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">3 / 9</gadget>
<output>1/3 = around 0.333333</output>

<result>1/3 = around 0.333333</result>