3 squares with side length 5 cm are put together to form a rectangle, what is the perimeter of the rectangle?
把3个边长是5厘米的正方形拼成一个长方形，这个长方形的周长是多少．
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">15 + 5</gadget>
<output>20</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>