Mastering Mathematics Smartly
by Wee Wen Shih

Students often find this topic hard to grasp. I like to recommend these resources that will help improve your understanding.

• This lesson page summarises important concepts of permutations & combinations and it also includes a homework page with selected solutions for the learner to review.
  
  
• This website encourages the learner to ask key questions before solving a counting problem.
  
  
• This set of notes highlights key results of permutations & combinations and features good examples for the learner to appreciate approaches to counting.
  
  
• This website explains approaches to solving counting problems through examples.

Is this topic applicable to real life? The answer is positive, according to this article that is both interesting and insightful.