Use rectangular pieces of paper with a length of 12cm and a width of 9cm to form a square. How many pieces should be used at least?
用长12cm，宽9cm的长方形纸片拼成正方形，最少要用多少张．
<gadget id="calculator">36 / 12</gadget>
<output>3</output>

<gadget id="calculator">36 / 9</gadget>
<output>4</output>

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

<result>12</result>