Topic 9.2 · Mathematics · Miscellaneous Topics

Permutations & Combinations

Permutations & Combinations is studied as part of "Miscellaneous Topics" (Advanced Topics) in Mathematics. Probability, permutations and combinations, calendars, clocks and age problems round out the syllabus.

In the examination context, permutations & combinations carries conceptual questions that test both factual recall and analytical understanding. Revise this topic in sequence with the rest of the chapter so that chronological and thematic links are clear.

Important Facts

Permutation: nPr = n!/(n−r)!
Combination: nCr = n!/r!(n−r)!
Odd days: Count of days beyond complete weeks
Probability: Favourable outcomes ÷ total outcomes

Key Points

Probability — Favourable outcomes ÷ total outcomes
Permutation — nPr = n!/(n−r)!
Combination — nCr = n!/r!(n−r)!
Odd days — Count of days beyond complete weeks

Important Names

Pierre de FermatBlaise Pascal

Exam-Oriented Notes

»nCr counts selections (order irrelevant), nPr counts arrangements. A century year is a leap year only if divisible by 400.