Teacher Wang plans to use square bricks with a side length of 3 decimeters to pave the classroom, which costs 720 yuan. Later, the square bricks with a side length of 4 decimeters were used. How many pieces should be used?
王老师计划用边长3分米的正方形砖铺教室，要720块．后来改用边长4分米的正方形砖，要用多少块？
<gadget id="calculator">720 * 3 * 3</gadget>
<output>6_480</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">6_480 / 16</gadget>
<output>405</output>

<result>405</result>