Xingxing Primary School beautifies the environment and paves the road with colored cement bricks. Paving the floor with square bricks with a side length of 20cm costs 3600 yuan. If you use square bricks with a side length of 30cm instead, how many pieces are needed?
星星小学美化环境，用彩色水泥砖铺路面．用边长20cm的方砖铺地，要3600块．如果改用边长为30cm的方砖铺，需要多少块？
<gadget id="calculator">20 * 20 * 3_600</gadget>
<output>1_440_000</output>

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

<gadget id="calculator">1_440_000 / 900</gadget>
<output>1_600</output>

<result>1_600</result>