A communication company installs telephones for the residents of Guangming Community. If they install 25 telephones per day, they can be installed in 18 days.
某通信公司为光明小区住户安装电话，如果每天安装25部，18天可以装完，如果想15天完成，平均每天要安装多少部？
<gadget id="calculator">25 * 18</gadget>
<output>450</output>

<gadget id="calculator">450 / 15</gadget>
<output>30</output>

<result>30</result>