The perimeter of a rectangle is 16 meters, and the ratio of length to width is 5:3. What is the area in square meters?
长方形的周长16米，长与宽比为5：3，面积是多少平方米．
<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">16 / 2 / 8</gadget>
<output>1</output>

<gadget id="calculator">5 * 1 * 3 * 1</gadget>
<output>15</output>

<result>15</result>