The school installed 9 lamps in each classroom of the newly built teaching building. The school has 4 floors, and each floor has 5 classrooms. How many lights should be installed in total?
学校给新建的教学大楼每个教室安装9盏灯．学校共有4层楼，每层有5个教室，一共要安装多少盏灯？
<gadget id="calculator">4 * 5 * 9</gadget>
<output>180</output>

<result>180</result>