Book Description
This booklet, part of the Exademy Series, is a dedicated practice guide for the UPSC CSAT exam, focusing specifically on the topic of Factorials. It is designed to help aspirants master this frequently tested concept, which is described as a "gatekeeper" for the UPSC Mains.

Rather than a dense textbook of theory, this guide serves as a "testing ground" to turn concepts into mastery through focused practice. It emphasizes clarity, accuracy, and speed to help students perform under pressure.

Key features include:

A Concise Concept Lecture on factorial basics, key formulas like Legendre's Formula, and advanced techniques.

An Exam Focus & Strategy section with time management advice and common trap-question patterns.

A Full Practice Set of 30 questions categorized by skill level (e.g., Trailing Zeros, Highest Power, Unit Digits).

Detailed Solutions & Explanations for every problem.

A Self-Assessment checklist and a Problem Coverage Matrix to track readiness.

After completing the booklet, aspirants will be able to calculate trailing zeros, find the highest power of any number that divides a factorial, determine unit digits of complex expressions, and translate word problems into factorial calculations.

About the Author
Prabhash Kumar is described as a social entrepreneur, multidisciplinary educator, and advocate for equity and inclusive leadership.

He has a distinguished academic background, having graduated as the Departmental Topper in both his B.Tech in Mechanical Engineering and his M.Tech at the National Institute of Technology (NIT) Rourkela. He was also a recipient of the prestigious Prime Minister's Research Fellowship (PMRF) at the Indian Institute of Technology (IIT) Kharagpur.

He has since transitioned from doctoral research to focus on societal transformation, completing an MBA in Human Resource Management, a B.Ed, and is pursuing M.A. degrees in Political Science and Economics. His profile is supplemented by advanced international certifications from universities in the United States and Europe, including the University of London and The Johns Hopkins University, with training in global diplomacy, equity, and pedagogy.

Guided by a philosophy of "paying back to society," Prabhash Kumar works as a Senior Teacher and Academic Administrator, dedicating his efforts to creating opportunities for marginalized communities. His focus includes LGBTQIA+ inclusion, mental health advocacy, and equitable access to education. He hails from Bhagalpur, Bihar.