Four identical small squares are put together to form a rectangle with a perimeter of 40 cm. What is the area of this rectangle in square centimeters?
四个完全一样的小正方形，拼成一个周长是40厘米的长方形，这个长方形的面积是多少平方厘米．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">40 / 2 / 5</gadget>
<output>4</output>

<gadget id="calculator">4 * 4 * 4</gadget>
<output>64</output>

<result>64</result>