It takes 180 square bricks with a side length of 30 cm to pave the floor of a house. If the square bricks with a side length of 20 cm are used instead, how many bricks are needed? (Solve with ratio)
铺一间房屋地面，用边长30厘米的方砖要180块，如果改用每块边长20厘米的方砖来铺，要多少块？(用比例解)
<gadget id="calculator">30 * 30 * 180</gadget>
<output>162_000</output>

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

<gadget id="calculator">162_000 / 400</gadget>
<output>405</output>

<result>405</result>