China Netcom installs telephones for the residents of Guangming Community. If 25 telephones are installed every day, the installation can be completed in 18 days. (Solution by proportional method)
网通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，平均每天要装多少部？(用比例方法解)
<gadget id="calculator">25 * 18</gadget>
<output>450</output>

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

<result>30</result>