At Sifu Faiza's Kung Fu School, kids learn to be strong and fast. They also learn to be smart, cool-headed, and honest. So Joy, Adam, Sam, and Amy are surprised when the key to the school is stolen--as well as all their kung fu gear. Now they'll have to use all kinds of calculations--addition, subtraction, multiplication, and division--to figure out the clues, follow the thieves, and find . . . The Lost Key.