This is the first book of Math Contest Books Series. The book introduces a powerful problem solving technique - the mass points method. The book can be used by students preparing for math competitions such as Mathcounts, AMC 10/12/AIME.
Second book of Math Contest Books Series:
https: //www.amazon.com/Balls-Boxes-Yongcheng-Chen/dp/1540390578
Third book of Math Contest Books Series: The Area Method
https: //www.amazon.com/dp/1540856410
Fourth book of Math Contest Books Series: Problem Solving Using Cauchy's Inequality
https: //www.amazon.com/dp/1541000285
Fifth book: the Completing Square Method: https: //www.amazon.com/dp/1542426626
9th book: Problem Solving Using Auxiliary Lineshttps: //www.amazon.com/dp/1975681754
10th book: https: //www.amazon.com/Problem-Solving-Using-Vietas-Theorem/dp/1542800056