The school uses floor tiles to pave the floor of the meeting room. Using floor tiles with an area of 9 square decimeters, 320 pieces are needed to cover them; if square floor tiles with a side length of 4 decimeters are used instead, how many pieces are needed to cover them?
学校用地砖铺会议室地面．用每块面积是9平方分米的地砖，需要320块才能铺满；如果改用边长是4分米的正方形地砖，需要多少块才能铺满？
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">320 / 16</gadget>
<output>20</output>

<gadget id="calculator">9 * 20</gadget>
<output>180</output>

<result>180</result>