The number of girls is less than that of boys (1/5), and the number of girls is equal to that of boys ((())/(())).
女生人数比男生少(1/5)，女生人数是男生的((())/(()))．
<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">(4/5) / 1</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>