A rectangle is 10 cm long and 5 cm wide, what is the perimeter of the rectangle in cm?
一个长方形长10厘米，宽5厘米，这个长方形周长是多少厘米．
<gadget id="calculator">10 + 5</gadget>
<output>15</output>

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

<result>30</result>