To pave a road with rectangular bricks 30 cm long and 24 cm wide, 900 bricks are needed. If you use square bricks with a side length of 20 cm instead, how many pieces are needed? (Solve with ratio)
用长30厘米，宽24厘米的长方形砖铺一条路，需用900块．如果改用边长20厘米的方砖铺，需用多少块？(用比例解)
<gadget id="calculator">30 * 24 * 900</gadget>
<output>648_000</output>

<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<gadget id="calculator">648_000 / 400</gadget>
<output>1_620</output>

<result>1_620</result>