Mathematics · Profit and Loss

A trader owns a faulty weighing scale where one pan is 300 grams heavier than the other. He uses a 2 kg weight while purchasing goods and a 5 kg weight while selling them. He always uses the defect in his favor — that is, while buying, he keeps the lighter pan under the goods, and while selling, he keeps the heavier pan under the goods. If he sells the goods at cost price per unit weight, what is his approximate profit percentage?