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Permutation & Combination

Question

There are few letters, namely “GIIILK”.

  1. How many different ways the words can be arranged in a row?
  2. How many ways of arrangement that all three letters of “I” are together?

Answer

  1. 20
  2. 6

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!)

About the Math Tutor - Dr Loo

I am a PhD holder with 8 years of teaching experience at secondary school and university. My expertizes are mathematics, statistics, econometrics, finance and machine learning.

Currently I do provide consultation and private tuition in Singapore. For those who are looking for math tutor in Singapore or statistics tutor in Singapore, please feel free to contact me at +65-85483705 (SMS/Whatsapp/Telegram).

Some of the math tuition in Singapore I provide includes O-level math tuition and also JC Math Tuition (H1 Math Tuition & H2 Math Tuition). On the other hand, my statistics tuition in Singapore mostly focus on pre-university level until postgraduate level. For those who prefer online tutoring service, the online O-level math tuition and online JC math tuition are also available.

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