The length of a rectangle is 16 cm. If the length is increased by 4 cm, how much should the width be reduced to keep the area of the rectangle constant?
一个长方形的长是16厘米，如果长增加4厘米，要使长方形的面积不变，宽应当减少多少
<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

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