If the width of a rectangle is 3 cm and the length is 5 times the width, what is the area of the rectangle?
一个长方形的宽是3cm，长是宽的5倍，长方形的面积是多少．
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<result>45</result>