The classroom is paved with square bricks, and 200 square bricks with an area of 18 square decimeters are needed. If square bricks with a side length of 3 decimeters are used instead, how many square bricks are needed?
教室用方砖铺地，用面积18平方分米的方砖需要200块，如果改用边长3分米的方砖，需要多少块？
<gadget id="calculator">18 * 200</gadget>
<output>3_600</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">3_600 / 9</gadget>
<output>400</output>

<result>400</result>