In a ratio, the two internal terms are the reciprocals of each other, if one external term is known to be (1/5), then what is the other external term.
在一个比例里，两个内项互为倒数，已知一个外项是(1/5)，则另一个外项是多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<result>5</result>