The width of a rectangle is 5 cm and the length is twice the width. What is the perimeter of the rectangle?
一个长方形的宽是5厘米，长是宽的2倍，这个长方形在周长是多少？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>