The floor of Xiaoming's dining room is 30dm long and 15dm wide, and it needs to be covered with square tiles with a side length of 3dm. How many tiles should be used at least?
小明家饭厅地面长30dm，宽15dm，要用边长是3dm的正方形瓷砖来铺满，至少要用这种瓷砖多少块？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">15 / 9</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">30 * (5/3)</gadget>
<output>50</output>

<result>50</result>