No. 5.
Two boys kept neighboring apple stands, and each had thirty apples to sell every day. One sold his at the rate of two for five cents, and received seventy-five cents, and the other at three for five cents, and received fifty cents, the total being one dollar and twenty-five cents. It happened one day that one of the boys was sick, and the other engaged to sell the whole stock of sixty apples at the same rate. "Two for five, and three for five, that's five for ten," said he, and five for ten he sold them. But to his astonishment, when he got through he had but one dollar and twenty cents instead of one dollar and twenty-five cents. Now how did he lose five cents?