To pave a room with floor tiles, 225 floor tiles with an area of 9dm**2 are needed. If floor tiles with a side length of 5dm are used instead, how many tiles are needed? (Solve with ratio)
用地砖铺一间房间，用面积9dm**2的地砖需要225块，如果改用边长是5dm的地砖铺，需要多少块？(用比例解)
<gadget id="calculator">9 * 225</gadget>
<output>2_025</output>

<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">2_025 / 25</gadget>
<output>81</output>

<result>81</result>