BOOK REVIEW An MIT Alum Reveals The Simple Art of Estimation

How Many Licks?

Aaron Santos ’01

Perseus Book Group

September 2009


Could you lift a house if only it were made of Styrofoam? Is it feasible to dig one’s way out of prison with a spoon? How many balloons might it actually take to lift a person or a house off the ground?

If these questions intrigue you, check out How Many Licks?, a book by physicist and MIT alumnus Dr. Aaron Santos that’s all about guessing. Santos not only provides you with the answers to many titillating questions, but he provides you with the tools to arrive at them yourself.

The book centers around the Fermi Method, whose statement is deceptively simple: make basic assumptions and estimates about what you want to know, and then combine them through calculation to find your answer. This sounds easy enough. If we want to know how many leaves are on a tree, we could estimate the number of leaves on a branch and the number of branches on the tree, and multiply these numbers together. But say we wanted to compute how many Big Bad Wolves it would take to blow down the little piggy’s brick house? Where would we start? What kind of information would we need? It’s not at all obvious, and these are the questions Santos tackles in this colorful text.

As an MIT Undergraduate with a strong background in math, I will admit that this book didn’t show me anything I hadn’t seen before. When I first picked up the book, I had a glimmer of hope that it would dazzle me with ingenious techniques for making quick, accurate estimates. I was disappointed — but that is hardly fair. How Many Licks? aims to appeal to the general public and in this it succeeds. Not only is the material in the book very accessible, but the friendly, spacious layout and the plentiful pictures (as well as the awesome examples) make it a very pleasurable and entertaining read. You can hate math and still like this book.

As such, I applaud the author’s effort to spread appreciation of and literacy of mathematics and bridge the gap between mathematicians and other people. Anyone who harbors a preconception that only those blessed to commune with the forces of mathematics can hope to divine the answers to questions like “How long of a line can you draw with one pen before it runs out of ink?” should totally read this book.

And even if the math is not new to you, How Many Licks? is still chock full of interesting inquiries and tidbits. Despite my lack of newly acquired math skills, I found the book engrossing and entertaining, and definitely worth at least a skim. That endearing MIT quirkiness is readily tangible with these pages. You’ll see what I mean when you read it.