Ask HN: Books to Keep Your Natural Sciences Skills Sharp

My father, who has degrees in electrical engineering and a master's in computer science, completed his studies in the 1960s. He has had a distinguished career as a software developer, IT director, and eventually retired as a territory manager for a prestigious company. For the past ten years, he has been teaching COBOL at a university. Now at 76, he is concerned about losing his natural science skills. I am looking for book recommendations (not apps) that offer daily exercises in math and physics for him. Ideally, these books would range from basic arithmetic to intriguing problem-solving exercises. Does anyone have any suggestions or ideas?