Math Olympiad Problems

While I started to teach Olympiad math as a volunteer in Williams Elementary School, San Jose, California, I could not find a low price book for a collection of Olympiad math problems. The existing reference books are pretty expensive. I decided to write one for the class by myself. Here comes this book!
This is a low price book for 4th to 8th grade students to learn Olympiad math at home. 28 different types of interesting math problems with reference answers are collected in this book for kids to practice at home.
Part of the problems in this book are also used while I teach Olympiad math to the GIFTED students in Williams.
But if you are looking for a book with detailed solutions, please buy
"Olympiad Math Weekly Practice" instead:
http://www.amazon.com/Olympiad-Math-Weekly-Practice-Cheney-ebook/dp/B009GW4TVE/ref=sr_1_7?ie=UTF8&qid=1446042822&sr=8-7&keywords=math+olympiad

I hope it can be of help for you. Thank you.
Cheney Gao