Use a square of 1 square centimeter to measure a rectangle. There are exactly 3 rows and 5 pieces in each row. What is the area of the rectangle?
用1平方厘米的正方形去量一个长方形，正好摆放了3排，每排摆放5个，这个长方形的面积是多少．
<gadget id="calculator">3 * 5 * 1</gadget>
<output>15</output>

<result>15</result>