Two identical rectangular pieces of paper fit together exactly to form a square with a perimeter of 40 cm. What is the perimeter of each rectangular piece of paper in centimeters?
两张同样的长方形纸片恰好可拼成一个周长40厘米的正方形，每张长方形纸片的周长是多少厘米．
<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">10 + 5</gadget>
<output>15</output>

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

<result>30</result>