Given:
Principal loan = $548,048
Exact interest = $50,000
Interest rate = 9%
Exact Interest = Principal * Interest rate * Time/365
Simply substitute each part of the equation by its value.
50,000 = 548,048 * 0.09 * t/365
50,000 * 365 = 49,324.32t
18,250,000 = 49,324.32t
18,250,000 / 49,324.32 = t
370 = t
It would take 370 days for a construction loan of $548,048 to earn $50,000 exact interest at 9% interest rate.