A street lamp installation team is responsible for the installation of street lamps on a road with a total length of 3.5 kilometers. It plans to install 20 lamps per day and complete the task in 15 days. Due to the improvement of work efficiency, the task was completed in only 10 days. How many more lamps are actually installed per day than originally planned?
某路灯安装队，负责一段全长3.5千米公路的路灯安装，计划每天安装20盏，15天完成任务．由于提高了工作效率，结果只用10天就完成了任务．实际每天比原计划多安装多少盏？
<gadget id="calculator">15 / 10</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">20 * (3/2)</gadget>
<output>30</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<result>10</result>