Find the rules and fill in the numbers: (1/2), (1/3), (2/5), (3/8), how many.
找规律填得数：(1/2)，(1/3)，(2/5)，(3/8)，多少．
<gadget id="calculator">5 / 13</gadget>
<output>5/13 = around 0.384615</output>

<result>5/13 = around 0.384615</result>