If the length of a rectangle is 5 decimeters and the width is 30 centimeters, what is the perimeter?
一个长方形的长是5分米，宽是30厘米，周长是多少．
<gadget id="calculator">30 / 10</gadget>
<output>3</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>