The length of a rectangle is 27 cm and the width is 15 cm. What is the perimeter of the rectangle?
长方形的长为27cm，宽为15cm，这个长方形的周长是多少．
<gadget id="calculator">27 + 15</gadget>
<output>42</output>

<gadget id="calculator">42 * 2</gadget>
<output>84</output>

<result>84</result>