Street-fighting mathematics
by Sanjoy Mahajan · first published 2010
66% recommend34% neutral
Why HN recommends it
Teaches educated guessing, Fermi-style estimation, dimensional analysis and approximation through intuitive real-world examples. Suits students and engineers who want sharper problem-solving instincts; free to read.
Summarised by Claude from recommending comments
In problem solving, as in street fighting, rules are for fools: do whatever works—don't just stand there! Yet we often fear an unjustified leap even though it may land us on a correct result. Traditional mathematics teaching is largely about solving exactly stated problems exactly, yet life often hands us partly defined problems needing only moderately accurate solutions. This engaging book is an antidote to the rigor mortis brought on by too much mathematical rigor, teaching us how to guess answers without needing a proof or an exact calculation. In Street-Fighting Mathematics, Sanjoy Maha
Affiliate links. As an Amazon Associate I earn from qualifying purchases.
Mentions per year
What Hacker News says
Related books
2014–2026The art of insight in science and engineering
Sanjoy Mahajan
Recommended by 11 · mentioned by 1411 recommend · 14 mention11 recommend · 1411 recommend
2011–2023Solving Mathematical Problems
Terence Tao
Recommended by 3 · mentioned by 43 recommend · 4 mention3 recommend · 43 recommend
2009–2025Guesstimation
John A. Adam
Recommended by 8 · mentioned by 98 recommend · 9 mention8 recommend · 98 recommend
2008–2025Mathematics for the Nonmathematician
Morris Kline
Recommended by 12 · mentioned by 1412 recommend · 14 mention12 recommend · 1412 recommend
2009–2021Algebra
Israel M. Gel'fand
Recommended by 5 · mentioned by 55 recommend · 5 mention5 recommend · 55 recommend
2009–2024The Art of Problem Solving
Richard Rusczyk, Sandor Lehoczky
Recommended by 32 · mentioned by 3832 recommend · 38 mention32 recommend · 3832 recommend
Secrets of mental math
Arthur Benjamin
Recommended by 12 · mentioned by 1512 recommend · 15 mention12 recommend · 1512 recommend
2012–2026Precalculus mathematics in a nutshell
George Finlay Simmons
Recommended by 10 · mentioned by 1110 recommend · 11 mention10 recommend · 1110 recommend
…is just as senseless as saying 1m=1=$1. It's true that abstract math often drops units because some things (like Taylor series) work nicely in certain units. That doesn't make the unit meaningless. Street-Fighting Mathematics, thesis/book by Sanjoy Mahajan, shows what amazing things you can die in abstract math if you don't forget units.
on “Turns are better than radians” ↗If you want to practice skills like these, try: Street-Fighting Mathematics [1] and The Art of Insight in Science and Engineering by Sanjoy Mahajan (MIT) [2]. Free downloads via: [1] https://mitpress.mit.edu/books/street-fighting-mathematics [2] https://mitpress.mit.edu/books/art-insight-science-and-engin...
on “The Dying Art of Mental Math Tricks” ↗Orwell's book's structure was dictated by the publishers, but I still love the content. My allusion was because I am wondering why the description needs to insult pure mathematics in order to promote Street Fighting Mathematics. And similarly to Orwell's book, it seems like Street Fighting Mathematics does actually have interesting content, despite whatever the reason may be that they need an "antidote" for general mathematics.
on “Street-Fighting Mathematics” ↗Free resource that has come up a few times on HN in the past: Street-Fighting Mathematics by Sanjoy Mahajan. https://mitpress.mit.edu/books/street-fighting-mathematics Click on "open access" to get to the PDF link.
on “What use is mental math in 2022?” ↗Try Street-Fighting Mathematics by Sanjoy Mahajan: https://direct.mit.edu/books/oa-monograph/5339/Street-Fighti...
on “Ask HN: Sources to learn powerful everyday useful mathematical concepts” ↗…however it is and keep pruning away at it until your solution is sculpted from the clay. It can and will happen. If you've ever tried doing Fermi Estimates (like those prescribed in https://www.amazon.com/Street-Fighting-Mathematics-Educated-... , https://www.amazon.com/Art-Insight-Science-Engineering-Compl... , https://web.archive.org/web/20160309161649/http://www.its.ca... , https://www.amazon.com/How-Measure-Anything-Intangibles-Busi...),…
on “Ask HN: Resources on how to improve abstract thinking skills?” ↗"Coolest" math book on my shelf (I'm a Math/CS Major) is "Street-Fighting Mathematics" by Sanjoy Mahajan. It's about "the art of educated guessing and opportunistic problem solving". The author used to teach these topics as a class at MIT.
on “Ask HN: Graduation Present for Aspiring Math Major?” ↗Reminds me of Louis Benezet's experimental elementary math education system (ca. 1930s), and Sanjoy Mahajan's Street Fighting Mathematics. What a clever idea.
on “A calculator that only shows the answer after you give a suitable estimate” ↗Street-Fighting mathematics, by Sanjoy Mahajan. It's the text to an MIT course [1]. There's a PDF of an older edition available for free [2]. [1] http://streetfightingmath.com/ [2] http://ocw.mit.edu/courses/mathematics/18-098-street-fightin...
on “Ask HN: What's the best math eBook you have read?” ↗…they're free. Yes, time is the biggest cost of any book. But there are some massively helpful [0], current [1] and legendary [2] books on this list. [0] Learn Python the Hard Way by Zed A. Shaw [1] Street-Fighting Mathematics by Sanjoy Mahajan [2] Structure and Interpretation of Computer Programs by Harold Abelson, Gerald Jay Sussman, Julie Sussman
on “The Hacker Shelf: Collection of free books for the intellectually curious” ↗Same for me. The book and its tools are extremely empowering. In general, anything from Sanjoy Mahajan (the author) is extremely insightful: -Street Fighting Mathematics -The Art of Insight in Science and Engineering -Lecture notes on signals & systems (a bit harder to find) -Lecture notes on thermodynamics (real-world insights rather than endless manipulations of weird…
on “Ask HN: What things have richly rewarded the time invested in mastering them?” ↗This comment has nothing to do with the submission other than its title reminded me of the title of another, quite different, math book which some people here might enjoy: "Street-fighting Mathematics" by Sanjoy Mahajan [1]. [1] https://mitpress.mit.edu/books/street-fighting-mathematics
on “Punk Mathematics (2010)” ↗…https://www.amazon.com/Method-Coordinates-Dover-Books-Mathem... the books by sanjoy mahajan are also a treat and teach real-world applications of mathematical and scientific thinking. https://www.amazon.com/Street-Fighting-Mathematics-Educated-... https://www.amazon.com/Art-Insight-Science-Engineering-Compl...
on “Mathematics for the Adventurous Self-Learner” ↗Street Fighting Mathematics, and The Art of Insight in Science and Engineering, both by Sanjoy Mahajan. You can find the PDFs online.
on “Problem Solving Techniques” ↗I highly recommend both books by Sanjoy Mahajan (who has a background in theoretical physics), especially “Street-Fighting Mathematics: The Art of Educated Guessing and Opportunistic Problem Solving”. http://www.sanjoymahajan.com/works.htm
on “John Urschel tackles his lifelong balance of math and football in new memoir” ↗