In a ratio, the two internal terms are reciprocals of each other, one of the external terms is 2.5, and the other external term is 2.5.
在一个比例中，两个内项互为倒数，其中一个外项是2.5，另一个外项是多少．
<gadget id="calculator">1 / 2.5</gadget>
<output>0.4</output>

<result>0.4</result>