When the circumference of a circle increases (1/2), its area increases by how much (expressed in fractions).
一个圆的周长增加(1/2)，它的面积就增加多少(用分数表示)．
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<result>5/4 = around 1.25</result>