## Solve Physics and Math Problems at Brilliant.org

I have shared quite a lot of sites in this blog about places where you can find challenging math problems for your intellectual satisfaction. In this post, I am going to introduce a website called Brilliant.org, a problem solving website which provides different levels of physics, computer science, and math problems depending on solver’s ability.

Brilliant.org provides different levels of physics and math problems, from practice to Olympiad level. Recently, it has also added problems in computer science particularly on data structures and algorithm. Math problems include challenges in algebra, number theory, geometry, and combinatorics. Physics problems include challenges in mechanics, electricity and magnetism.

Just like in other challenges and games, problem solved at Brilliant.org have corresponding points. Players can exchange points for corresponding prizes. Players can also discuss problems within the website.

## Free Statistics, Combinatorics, Probability Ebooks

Are you looking for free math ebooks? Below are the free and downloadable statictics, combinatorics, and probability ebooks in PDF and other formats.  I am going to update the list from time to time so you might want to bookmark this page. For more free math ebooks and other freebies, please visit the Algebra and Trigonometry, Geometry and Topology, and Calculus and Analysis.  For other freebies, please visit the All for Free page.

1. An Introduction to Probability and Random Processes by Kenneth Baclawski and Giancarlo Rota
2. Directions in Infinite Graph Theory and Combinatorics by Reinhard Diestel
3. Introduction to Probability and Statistics for Linguistics by Marcus Kracht
4. Introduction to Probability and Statistics Using R by Jay Kerns
5. Introduction to Probability by Charles Grinstead
6. Introduction to Probablity and Statistics (Notes) by Muhamma El Taha
7. Introduction to Probability Theory by Christel Geiss and Stefan Geiss
9. Probability and Statistics Cookbook by Matthias Valentine
10. Probability, Statistics and Stochastic Processes (Notes) Cosma Rohilla Shalizi
11. Probability Theory: The Logic of Science by E.T. Janes
12. Think Stats: Probability and Statistics from Programmers by Allen b. Downey

Online

1. Concepts and Applications of Inferential Statistics by Richard Lowry
2. CK-12 Basic Probability and Statistics by Brenda Meery
3. Statistics, Probability, and Game Theory by T.S. Ferguson, L.S. Shapley, J.B. MacQueen

## 8 Amazing Mechanical Calculators Before Modern Computers

Before there are graphing calculators, spreadsheets and computer algebra systems, mathematicians and inventors searched for solutions to ease the burden of calculation. Today we celebrate human achievement in creating these calculators. Below are the 8 mechanical calculators before modern computers were invented.

##### 1. Abacus (ca. 2700 BC)

Although abacus is not mechanical, it was one of the most widely used calculating device for many years.  The abacus is one of the earliest counting machines used for arithmetic calculations. It made up of beads and frame. It was particularly used Japan, India and China. Although they are popular in Asia, the abacus has a long history which originated 2700 years ago in Sumeria. It was also used in Egypt, Persia (Iran), and Greece.  The reason why the abacus is popular was probably because it’s very easy to use. Until now, there are still people who use this ancient tool. » Read more

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