## Nonplussed! Review

"Nonplus" is not a particularly common English word so I looked it up on dictionary.com.

–verb (used with object)

1. to render utterly perplexed; puzzle completely.

–noun

2. a state of utter perplexity.

"Nonplussed" is a book full of perplexing facts, and solid Math to explain the perplexities. In other words, this book is about mathematically provable facts that don't actually seem to be true.

Here is a great example of the state of being nonplussed and my favorite part of the book. Chapter 13 is all about Friday the 13th. Many of know that every year has at least one Friday the 13th. But, did you know that the 13th day of any month falls more frequently on a Friday than on any other day of the week? Did you know that the first day of any year ending in "01" (e.g. 1901, 2001) cannot fall on a Friday (or Wednesday or Sunday either)? These are some interested facts explored and proven in this one of fourteen chapters.

Chapter 14 is my second favorite chapter. It dives into a brilliant idea by John Conway -- a procedure that produces all prime numbers by operating on a set of 14 improper fractions. The chapter explains how Conway's novel invention is a very cleverly disguised programming language that cranks out prime numbers the way a computer might.

Another interesting chapter is Chapter 3. It's about the birthday paradox. If you have 23 people in a room then there's a greater than 50% chance that two of them will share a birthday (ignoring leap years.) Many of us know this problem and have worked out the straightforward probability to prove it. But, Julian Havil, author of Nonplussed! goes further. How many people does it take for the chances of three of them having the same birthday to be more than 50%? What about the chances of two or more people having birthdays that are two days apart? These generalizations are not easy but they're rewarding to explore.

The problems are interesting, the Math is comprehensive although not trivial. It takes dedication to follow the explanations. But, it's worth the effort for the great insights that come from proving the non-obvious!

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