10,000 Subtraction Problems Practice Workbook: Improve Your Math Fluency Series
Chris McMullen is a physics instructor at Northwestern State University of Louisiana.  He earned his Ph.D. in phenomenological high-energy physics (particle physics) from Oklahoma State University in 2002. Originally from California, he earned his Master's degree from California State University, Northridge, where his thesis was in the field of electron spin resonance.  As a physics teacher, Dr. McMullen observed that many students lack fluency in fundamental math skills. In an effort to help students of all ages and levels master basic math skills, he has published this Improve Your Math Fluency Series of math workbooks on arithmetic, fractions, and algebra.