Oxygen accounts for about 1/5 of the total volume of air. What percentage of the volume of oxygen is equivalent to the volume of other gases in the air?
氧气约占空气总体积的(1/5)，氧气的体积相当于空气中其它气体体积的百分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/5) / (4/5)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>