To build a small water conservancy project, the estimated investment is 45 million yuan, which is actually 1/5 less than the plan. How much yuan was actually used to build this project?
修建一座小型水利工程，预计投资4500万元，实际比计划节约了(1/5)，修建这项工程实际用了多少万元？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">4_500 * (4/5)</gadget>
<output>3_600</output>

<result>3_600</result>