This is a great book. It's filled with shortcuts that kids and adults alike can use. I expect my daughter to make use of some of the techniques when she takes the ACT this June. Because it speeds calculation it should save her some time. Now it's more like a game when we go shopping and I ask "what is the sales tax" or "hey tell me 45x45...come on quick." She rises to the challenge. Good book. Shortcuts are there that everyone can use to some degree.