The number of boys is the number of girls (4/5), how much more girls than boys.
男生人数是女生的(4/5)，女生比男生多多少．
<gadget id="calculator">5 - 4</gadget>
<output>1</output>

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

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