I love math. And, I have always been curious on how some people multiply, divide and subtract so quickly in their heads. When I was in high school, there was a group of people that were in a club sponsered by a teacher. Its name was "Number Semse". I could not participate because I had to work after school. This book exposed all of the secrets of this group. This is a great book on math tricks. I intent to share it with the elementary school student in my neighborhood.