On July 21, 2012, Beijing suffered heavy rainfall in the past 61 years, and some areas were seriously affected by flash floods. After the floods, post-disaster reconstruction was carried out in various places. A reconstruction building has 6 floors, 4 units, and a total of 216 households. How many households live in each unit per floor?
2012年7月21日，北京遭遇61年来强降雨，部分地区受山洪影响严重，洪灾后各地展开灾后重建．一座重建楼有6层，4个单元，共住有216户．每个单元每层住多少户？
<gadget id="calculator">216 / 4 / 6</gadget>
<output>9</output>

<result>9</result>