If the length of a rectangle is 60 cm and its width is 20 cm, what is its perimeter in cm?
一个长方形长是60厘米，比宽多20厘米，它的周长是多少厘米．
<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<gadget id="calculator">60 + 40</gadget>
<output>100</output>

<gadget id="calculator">100 * 2</gadget>
<output>200</output>

<result>200</result>