From the author of I Don`t Want to Be a Frog comes a hilarious new picture book that asks readers to solve one very important mysteryIt`s Mr. Tortoise`s birthday, and he can`t wait to eat cake with his friends. But there`s a hitch! Mr. Tortoise can`t remember how old he is, so his friends don`t know how many candles to put on the cake. And they won`t stop (or slice) until they figure out the mystery.Could Mr. Tortoise be as many years old as there are sections on his shell? He`s twice as big as the smaller tortoise . . . so is he twice as old? After the partygoers work through a variety of possibilities, they find their way to the answer with a simple bit of addition.With text from I Don`t Want to Be a Frog author Dev Petty and hilarious graphic novel-style illustrations from Ruth Chan, How Old Is Mr. Tortoise? will have readers guessing the answer from beginning to end.