Now there are some rectangular cards with a length of 10 cm and a width of 6 cm. At least how many such cards are needed to form a square.
现在有一些长10厘米，宽6厘米的长方形卡片，至少需要多少张这样的卡片才能拼出一个正方形．
<gadget id="calculator">2 * 3 * 5</gadget>
<output>30</output>

<gadget id="calculator">30 / 10</gadget>
<output>3</output>

<gadget id="calculator">30 / 6</gadget>
<output>5</output>

<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>