A pillowcase is 5 decimeters long and 4 decimeters wide. If you put lace around it, how many decimeters of lace will you need at least?
一只枕套长5分米，宽4分米，如果在它的四周镶上花边，至少需要多少分米的花边．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>