Thomas Canavan 
Mental Math [PDF ebook] 

All 50 of the fun and engaging puzzles in this book are carefully designed to help young readers hone their mental math problem solving abilities, increase their speed, confidence, accuracy, and ability in solving mental math problems both in the classroom and in real life. Each page of the book features a different puzzle intended to enhance the development of necessary mental math problem solving skills. The book’s content and methods correlate closely with National Council of Teachers of Mathematics (NCTM) standards.