A rectangle is 5 cm long and 4 cm wide, what is its perimeter in cm?
一个长方形长5厘米，宽4厘米，它的周长是多少厘米．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

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

<result>18</result>