For many, math is just a bad memory from grammar school. Yet, basic math is an important tool in everyday life. Teach Yourself Basic Mathematics takes the fear out of numbers with day-to-day examples from work, shopping, and home. Learn how to convert measurements between systems; understandfractions, decimals, and percentages; and make sense of graphs and tables.
A nice study guide for middle-school-level math written for adults. Includes lots of explanations on why the principles are true and has several brain teasers and logic puzzles. Is written from a British perspective, so Americans might find some examples hard to understand due to the framing.