7 students randomly stand in a row, what is the probability that A is standing in the middle?
7名同学任意站成一排，甲恰好站在中间的可能性是多少．
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<result>1/7 = around 0.142857</result>