In a ratio, the two inner terms are reciprocals of each other, one of the outer terms is (1/3), and the other is how much.
一个比例里，两个内项互为倒数，其中一个外项是(1/3)，另一个外项是多少．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<result>3</result>