Best Book for Maths Olympiad Class 6th:

1. "Math Olympiad Contest Problems for Elementary and Middle Schools" by George Lenchner:
This book is highly recommended for students preparing for Maths Olympiad in 6th grade. It contains a wide variety of challenging problems that are suitable for students at the elementary and middle school levels. The book covers various topics such as number theory, geometry, algebra, and combinatorics, which are essential for Olympiad preparation.

2. "Challenge Math For the Elementary and Middle School Student" by Edward Zaccaro:
This book offers a collection of engaging and thought-provoking math problems that will help students develop their problem-solving skills. It covers a wide range of topics and is designed to challenge students at the elementary and middle school levels. The book also provides detailed solutions to help students understand the concepts better.

3. "Math Olympiad Contest Problems for Elementary and Middle Schools" by Andrew Shulte:
This book is another excellent resource for students preparing for Math Olympiad in 6th grade. It contains a series of challenging problems that will help students sharpen their problem-solving skills and improve their mathematical abilities. The book covers various topics such as algebra, geometry, number theory, and combinatorics.
In conclusion, these three books are highly recommended for students preparing for Math Olympiad in 6th grade. They provide a comprehensive coverage of the topics and offer a wide range of problems to help students practice and improve their mathematical skills. Students can choose any of these books based on their preferences and learning style.