A classroom is paved with square bricks with a side length of 4dm, and 400 pieces are needed. If you use square bricks with a side length of 5dm instead, how many pieces are needed (use a proportional solution)?
一间教室用边长4dm的方砖铺，需要400块．如果改用边长5dm的方砖铺，需要多少块(用比例解)？
<gadget id="calculator">5 * 5 * 400</gadget>
<output>10_000</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">10_000 / 16</gadget>
<output>625</output>

<result>625</result>