Answer:
In the book "A Wrinkle in Time" by Madeleine L'Engle, Charles Wallace uses a strategy of reciting the multiplication tables to prevent himself from getting hypnotized by IT, the evil brain that controls the planet Camazotz.
By focusing on the logical and mathematical task of reciting the multiplication tables, Charles Wallace is able to resist the hypnotic influence of IT, which seeks to control his mind and make him conform to its will. This strategy is effective because it engages his mind in a different type of mental activity, preventing IT from gaining control over his thoughts and actions.