The school plans to pave classroom floors with square bricks. If square bricks with a side length of 2 decimeters are used, 1,800 pieces are needed. If square bricks with an area of 9 decimeters are used instead, how many pieces are needed? (Solve with ratio)
学校计划用方砖铺教室地面．如果用边长2分米的方砖，需要1800块，如果改用面积为9分米的方砖，需要多少块？(用比例解)
<gadget id="calculator">2 * 2 * 1_800</gadget>
<output>7_200</output>

<gadget id="calculator">7_200 / 9</gadget>
<output>800</output>

<result>800</result>