Jimmy and Tommy went off on their bikes for a picnic in the woods.
They had one bottle of lemonade between them. Jimmy went to explore while Tommy unpacked the food. When he returned, he found the bottle was empty.
"Hey!" he exclaimed crossly. "Half of that was mine!"
"I know," said Tommy, "but I was thirsty, and as my half was at the bottom of the bottle, I had to drink through yours to get to it."