A rectangle is scaled down by 1:3 and drawn on the drawing. If the length on the drawing is 5cm and the width is 4cm, what is the actual area of the rectangle?
把一个长方形按1：3缩小后画在图纸上，量得图上长是5cm，宽是4cm，则这个长方形的实际面积是多少．
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">15 * 12</gadget>
<output>180</output>

<result>180</result>