Maria's cost of sales for the year ended 31 December 2015 was $384,000. She marks up her goods sold by 33⅓% on cost. What was her gross profit for the year?

Selling price = cost × (1 + 1/3) = $384,000 × 4/3 = $512,000. Gross profit = Selling price − Cost of sales = $512,000 −$384,000 = $128,000 (equivalently, a 33⅓% mark-up on cost gives gross profit equal to one third of cost of sales, not a smaller fraction such as a fifth, a quarter, or three tenths of cost).