It takes 1800 pieces to pave the classroom with square bricks with a side length of 20cm; how many bricks are needed if the floor is paved with square bricks with a side length of 30cm?
用边长是20cm的方砖给教室铺地，需要1800块；如果改用边长30cm的方砖铺地，需要多少块砖？
<gadget id="calculator">20 * 20 * 1_800</gadget>
<output>720_000</output>

<gadget id="calculator">30 * 30</gadget>
<output>900</output>

<gadget id="calculator">720_000 / 900</gadget>
<output>800</output>

<result>800</result>