Hmm, Jim thought, that man in the store made me taller. Why can't I do that again?
With that thought, he said "Control my height!" and blew into the balloon!
FWOOOF! Jim felt a little dizzy as he gained 5 inches in height. At 5'5", he now around the same height as his classmates. He blew again.
FWOOOOF! Jim blew more into the balloon. He gained even more upwards height, getting 6 inches and rising to 5'11". He now had his dad's height, but Jim wasn't content.
FWOOOOOOOOF! Jim blew his hardest breath ever. The effort paid off. He shot up 7 inches to 6'6".
The world looked very different from 18 inches higher, he decided.