If three squares with side lengths of 5 cm are put together to form a rectangle, what is the perimeter of the rectangle in cm?
把三个边长都是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厘米．
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

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

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

<result>40</result>