The height of 15 dictionaries stacked together is 168 mm. If the height of 504 mm is stacked with the same dictionary, how many dictionaries are needed?
15本字典摞在一起高168毫米，如果用同样的字典摞504毫米的高度，需要几本这样的字典？
<gadget id="calculator">168 / 15</gadget>
<output>56/5 = around 11.2</output>

<gadget id="calculator">504 / (56/5)</gadget>
<output>45</output>

<result>45</result>