Great math tricks: How to perform fast calculation in head without a calculator

This book presents ways to perform fast calculations. Chapter 1 - Introduction. Chapter 2 - Time Table - This chapter presents the times table up to 25. Chapter 3 - Square - This chapter presents the squares of numbers up to 25. Then, it presents how square of numbers ending with 0, starting with 1 and ending with all 0's, comprising of all 1's, comprising of all 9's and ending with 5. Chapter 4 - Divisibility - This chapter presents ways to detect divisibility up to number 11.