Street-fighting Mathematics: The Art Of Educate... – No Sign-up

Sanjoy Mahajan's Street-Fighting Mathematics: The Art of Educated Guessing and Opportunistic Problem Solving is available as a free, open-access publication under a Creative Commons license. The text covers foundational tools for estimation and problem-solving, including dimensional analysis, easy cases, and pictorial proofs. Access the official open-access monograph from MIT Press direct.mit.edu or download the PDF via MIT OpenCourseWare ocw.mit.edu.