Kjartan Poskitt. Awesome Arithmetricks (Murderous Maths). New York, Scholastic, 1998.

Find out how to count your way out of a death-trap, why multiplication can stop a hairy green spot epidemic, and meet the barmy pure mathematicians who spent years proving 5 + 0 = 5. Meanwhile, Chainsaw Charlie, Halfsmile and their gang discover that even the simplest maths can be murderous.