A factory originally planned to have 100 workers complete a project. After 15 days of the project, due to technological innovation, the average work efficiency per person increased by 50%. As a result, the project was completed 25 days earlier than the original plan. project. How many days was originally planned to complete the project?
某工厂原计划由一百名工人来完成一项工程，当工程进行了十五天后，由于进行了技术革新，每人平均工效提高了50%，结果比原计划提前了25天完成了这项工程．问原计划完成这项工程需要多少天？
<gadget id="calculator">100 * 15</gadget>
<output>1_500</output>

<gadget id="calculator">100 * 25</gadget>
<output>2_500</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">100 * (1/2) * 15</gadget>
<output>750</output>

<gadget id="calculator">100 * (1/2) * 25</gadget>
<output>1_250</output>

<gadget id="calculator">1_250 - 1_500</gadget>
<output>-250</output>

<gadget id="calculator">1_500 + 2_500 + 750 + (-250)</gadget>
<output>4_500</output>

<gadget id="calculator">100 * (1/2)</gadget>
<output>50</output>

<gadget id="calculator">50 - 100</gadget>
<output>-50</output>

<gadget id="calculator">100 + (-50)</gadget>
<output>50</output>

<gadget id="calculator">4_500 / 50</gadget>
<output>90</output>

<result>90</result>