There are 4 yellow balls and 8 white balls of the same size in a box, what is the probability of touching the yellow ball?
一个盒子里有同样大小的黄球4个和白球8个，摸到黄球的可能性是多少．
<gadget id="calculator">4 + 8</gadget>
<output>12</output>

<gadget id="calculator">4 / 12</gadget>
<output>1/3 = around 0.333333</output>

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