piece of iron wire can just enclose a square with a side length of 4 decimeters. If this wire is used to form a rectangle with a length of 5 decimeters, what is the area of the rectangle?
一根铁丝正好能围成一个边长为4分米的正方形，如果用这根铁丝围成一个长为5分米的长方形，这个长方形的面积是多少平方分米？
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">8 - 5</gadget>
<output>3</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>