Mathcounts State Competition Preparation Volume 1 (Mathcounts State Competition Preparation 5 Volumes);

The books (Volumes 1 to 5) can be used by 5th to 8th grade students preparing for Mathcounts State and National Competitions.

Each chapter consists of (1) basic skill and knowledge section with plenty of examples, (2) exercise problems, and (3) detailed solutions to all problems.
Training class is offered: http://www.mymathcounts.com/Copied-2015-Mathcounts-State-Competition-Online-Training-program.php