One day, Xiaohua went to a residential building to do a social survey. This building has 15 floors, each floor has 35 windows, and every two households have 5 windows. If each household needs a questionnaire, Xiaohua must bring at least how many copies of the questionnaire.
一天，小华去一栋居民楼做社会调查．这栋楼有15层，每层有35个窗户，每两户人家有5个窗户．若每户人家需要一份调查表，则小华至少要带调查表多少份．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">35 / (5/2)</gadget>
<output>14</output>

<gadget id="calculator">15 * 14</gadget>
<output>210</output>

<result>210</result>