In a ratio, the two inner terms are reciprocals of each other, one of the outer terms is 2, and the other is how much.
在一个比例中，两个内项互为倒数，其中一个外项是2，另一个外项是多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>