Permutations and Combinations is a wonderful topic to prepare for and is a fun topic if done the right way. The entire chapter on Combinatorics from the book on
Quantitative Aptitude for CAT is available for free
here .
As an author, I quite enjoyed the challenge of creating questions for this topic and was pleased with the way the chapter turned out as well. This is considered a tricky topic by many CAT aspirants and so I was keen to have this as the free sample topic.
Please send any feedback you have on this topic (and/or the book) to prep@2iim.com.
The book can be bought at Flipkart through this
link .