In a ratio, the two inner terms are reciprocals of each other, one of the outer terms is (5/2), 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(5/2)，另一个外项是多少．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">1 / (5/2)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>