Before we found Two Plus Two is Not Five, we tried at least half a dozen learning systems and workbooks to teach math to our 4 year-old son. But we found that he was not able to learn much from them other than counting up the numbers on his fingers or pictures on the page. Then we happened upon the Two Plus Two is Not Five system. From the start, he has mastered the tricks easily. As part of the exercises, he has learned a number of new skills including counting backwards, counting by twos and adding/subtracting doubles. The system of learning the trick, practicing, and then doing the mixed exercises has quickly reinforced the learning and helped us immediately spot weaknesses in learning that we worked with him to correct. The structure of the book makes it easy to sit down with him, walk him through the tricks, and let him practice until he masters the skills. There is limited parental preparation involved, and we go through one page a night, five nights a week.