If the length of a rectangle is increased by 1/4, how much must the width be reduced in order to keep its area constant?
一个长方形的长增加(1/4)，要使它的面积不变，宽要减少多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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