Claudia Zaslavsky 
Number Sense and Nonsense [PDF ebook] 

These 80-plus math activities and number games help kids to think critically about math instead of just memorizing rules. The emphasis is on the underlying relationships between numbers and the process of manipulating them. Kids get together and play games with odd and even numbers, prime and composite numbers, factors, divisors, and multiples of numbers, common and decimal fractions. Children learn the history of numbers-finger counting, number symbols in various cultures, and different ways of calculating. The book is full of riddles, puzzles, number tricks, and calculator games. Kids develop skills in estimation and computation as they become familiar with the characteristics and behavior of numbers. They will gain math confidence and be ready to take chances, find their own errors, and challenge their peers.