The older brother is 25% heavier than the younger brother, and the younger brother is lighter than the older brother by how much
哥哥比弟弟重25%，弟弟比哥哥轻多少
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(1/4) / (5/4)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>