In a ratio, two inner terms are reciprocals of each other, and one outer term is (2/9), then what is the other outer term.
在一个比例里，两个内项互为倒数，一个外项为(2/9)，则另一个外项为多少．
<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>