In a ratio, the two internal terms are reciprocals of each other, one external term is (11/13), and the other external term is how much.
在一个比例里，两个内项互为倒数，一个外项是(11/13)，另一个外项是多少．
<gadget id="calculator">11 / 13</gadget>
<output>11/13 = around 0.846154</output>

<gadget id="calculator">1 / (11/13)</gadget>
<output>13/11 = around 1.181818</output>

<result>13/11 = around 1.181818</result>