Cut a circle with a diameter of 4 cm into an approximate rectangle, what is the perimeter of the rectangle in cm?
把一个直径是4厘米的圆剪拼成一个近似的长方形，这个长方形的周长是多少厘米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">6.28 + 2</gadget>
<output>8.28</output>

<gadget id="calculator">8.28 * 2</gadget>
<output>16.56</output>

<result>16.56</result>