In a ratio, the two outer terms are reciprocals of each other, one of the inner terms is (9/2), and the other inner term is how much.
在一个比例中，两个外项互为倒数，其中一个内项是(9/2)，另一个内项是多少．
<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">1 / (9/2)</gadget>
<output>2/9 = around 0.222222</output>

<result>2/9 = around 0.222222</result>