A rectangular floor has a length of 72 cm and a width of 18 cm. To lay a square with this kind of floor, at least how many pieces of this kind of floor should be used?
一种长方形地板的长是72厘米，宽是18厘米．用这种地板铺成一个正方形，至少要用多少块这样的地板？
<gadget id="calculator">2 * 2 * 18</gadget>
<output>72</output>

<gadget id="calculator">72 / 72</gadget>
<output>1</output>

<gadget id="calculator">72 / 18</gadget>
<output>4</output>

<gadget id="calculator">1 * 4</gadget>
<output>4</output>

<result>4</result>