In a ratio, the two internal terms are reciprocals of each other, one external term is (3/5), 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(3/5)，另一个外项是多少．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / (3/5)</gadget>
<output>5/3 = around 1.666667</output>

<result>5/3 = around 1.666667</result>