Likable, clever, and inventive sixth-graders Rufus Mayflower and Kate Makinstrey develop and sell toothpaste to become millionaires in just one year! When Rufus decides that toothpaste costs too much, he starts his own toothpaste making business. From his meager beginnings with re-used baby food jars up to a fully professional operation with stockholders and a tube-filling machine, he rakes in the cash and confounds the leaders of the pharmaceutical industry with his methods. This fun, breezy story includes many real-life mathematical problems which the characters must solve to succeed in their budding business.