The playground of Wenquan Elementary School is paved with square bricks. If square bricks with a side length of 2.5 decimeters are used, 3200 pieces are needed. If you use square bricks with a side length of 4 decimeters instead, how many square bricks only need to be purchased?
温泉小学用方砖铺操场．若用边长是2.5分米的方砖，需3200块．若改用边长为4分米的方砖来铺，只需购买多少块方砖就行了？
<gadget id="calculator">2.5 * 2.5 * 3_200</gadget>
<output>20_000</output>

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

<gadget id="calculator">20_000 / 16</gadget>
<output>1_250</output>

<result>1_250</result>