In a ratio, the two internal terms are reciprocals of each other, one external term is 0.2, 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0.2，另一个外项是多少．
<gadget id="calculator">1 / 0.2</gadget>
<output>5</output>

<result>5</result>