The two outer terms of a ratio are reciprocals of each other, one inner term is (1/5), and the other inner term is how much.
一个比例的两个外项互为倒数，一个内项是(1/5)，另一个内项是多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / (1/5)</gadget>
<output>5</output>

<result>5</result>