To build a teaching building, the original plan was to invest 2 million yuan, but the actual investment was 1.8 million yuan after the improvement plan. What percentage was saved compared to the original plan?
修建一座教学大楼，原计划投资200万元，改进方案后实际投资180万元，比原计划节省了百分之几？
<gadget id="calculator">200 - 180</gadget>
<output>20</output>

<gadget id="calculator">20 / 200</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>