The construction project of Metro Line 1 in a certain city has completed an investment of about 1.58 billion yuan this year, and the total amount of investment that needs to be invested is about 590 million yuan less than this year's three times.
某市地铁一号线建设项目今年约完成投资15.8亿元，还需投资的总额约比今年的3倍少5.9亿元，还需投资多少亿元？
<gadget id="calculator">15.8 * 3</gadget>
<output>47.4</output>

<gadget id="calculator">47.4 - 5.9</gadget>
<output>41.5</output>

<result>41.5</result>