The four classes of the fifth grade of Yucai Primary School held a football match, and every two classes were divided into one group, and the group was determined by drawing lots. What is the probability that Class 5 1 and Class 5 2 are in one group?
育才小学五年级四个班开展足球比赛，每两个班分成一组，抽签决定分组．五1班和五2班分在一个组的可能性是多少．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<result>1/6 = around 0.166667</result>