The Phantom Tollbooth
"That's absurd," objected Milo, whose head was spinning from all the numbers and questions.
"That may be true," he acknowledged, "but it's completely accurate, and as long as the answer is right, who cares if the question is wrong? If you want sense, you'll have to make it yourself." (14.34-35)
"Splendid," cried the Dodecahedron. "And suppose you had something and added less than nothing to it. What would you have then?"
"FAMINE!" roared the anguished Humbug, who suddenly realized that that was exactly what he'd eaten twenty-three bowls of. (15.27-28)
"There's nothing to it," they all said in chorus, "if you have a magic staff." Then six of them canceled themselves out and simply disappeared.
"But it's only a big pencil," the Humbug objected, tapping at it with his cane.
"True enough," agreed the Mathemagician; "but once you learn to use it, there's no end to what you can do." (15.37-39)