If the number of girls accounts for 2/5 of the whole class, then the number of boys is equal to the number of girls
女生人数占全班人数的(2/5)，则男生人数相当于女生人数的多少
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) / (2/5)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>