A fruit merchant bought some bananas. One fifth of them got rotten and were thrown away. He sold two fifths of the bananas with him at 15% profit and the remaining bananas at 10% profit. Find his overall loss or profit percent?

Let total bananas = 100. Rotten = 20, remaining = 80. First 2/5 sold means 40 bananas at 15% profit. Remaining 40 sold at 10% profit. Cost price of each banana = C. Total cost = 100C. Revenue from first 40 = 40C × 1.15 = 46C. Revenue from remaining 40 = 40C × 1.10 = 44C. Total revenue = 90C. Total cost = 100C. Loss = 10C on investment of 100C, which is 10% loss.