A child enters an ice cream parlor and sits at the table, the waitress approaches him to ask what he wants, the child asks "How much does a big ice cream cost?" The waitress answers "2 euros" the child takes out of his pockets some coins and accounts, had just 2 euros so he asks the waitress again "and the medium?" She quickly responds "That costs one euro and seventy-five cents" Upon hearing the response the child orders a medium ice cream.
When finished eating the ice cream the child leaves and the waitress comes to clean the table for when another customer arrives and discovers something that leaves her speechless, right there under the account were 25 cents, his tip.