Permutation & Combination
When learning the concept of permutation and combination in JC H2 Math Classes, you will come across some interesting concepts like the number of arrangement of objects in a line. In addition, you will learn how to calculate the number of arrangement of objects in circle. These concept will also take into account of cases like repetition and restriction.
Permutation Formula
n!/(n-r)!
This formula calculates the number of permutations of n things taken r at a time
Combination Formula
n!/[(n-r)!r!]
This formula calculates the number of combinations of n things taken r at a time
Number of permutations of n things when there are n1, n2, …, nk repeated items.
n!/(n1!n2!…nk!)
Question
There are few letters, namely “GIIILK”.
- How many different ways the words can be arranged in a row?
- How many ways of arrangement that all three letters of “I” are together?
Answer
- 20
- 6
About the Singapore Math Tutor - Dr Loo
I am a PhD holder with 9 years of teaching experience on teaching quantitative subjects at secondary school and university levels. My expertise are mathematics, statistics, econometrics, finance and machine learning.
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