In a ratio, the product of two outer terms is 2, and one inner term is (2/5), then what is the other inner term.
在一个比例中，两外项之积为2，其中一个内项为(2/5)，则另一个内项是多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<result>5</result>