The Missing Number Challenge or Operator Challenge: 500 Math/Logic Puzzles to Sharpen Your Mental Math Skills (Brain Boosting Puzzles, Band 3)

Brain Boosting Math Cross Puzzles.: 90+ Logic Based Puzzles to Sharpen Your...

The Sudoku Book: Brain-Boosting Number Puzzles to Challenge Your Logic and Concentration

Math Crosswords Challenge Book.: Engaging Number Puzzles That Strengthen Logic, Improve Skills,...

Cross Math: Math Maze and Conquer, Volume 2: More Brain Boosting Puzzles...