If the length of a rectangle is increased by 2 centimeters and the width remains the same, how many centimeters will the perimeter be increased?
一个长方形如果长增加2厘米，宽不变，那么周长增加多少厘米．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>