To pave a piece of ground, 200 square bricks with an area of 0.25 decimeters are needed. If square bricks with a side length of 0.4 decimeters are used instead, how many bricks are needed?
铺一块地面，用面积0.25平方分米的方砖需要200块，如果改用边长0.4分米的方砖，需要多少块？
<gadget id="calculator">0.25 * 200</gadget>
<output>50</output>

<gadget id="calculator">0.4 * 0.4</gadget>
<output>0.16</output>

<gadget id="calculator">50 / 0.16</gadget>
<output>312.5</output>

<result>312.5</result>