A rectangle has a perimeter of 40 cm and its length is four times its width. What is the area of this rectangle in cm**2.
一个长方形的周长是40cm，长是宽的4倍．这个长方形的面积是多少cm**2．
<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>