# Permutation & Combination

**Permutation & Combination (Question)**

You are asked to arrange the letters of “GEEEKL” differently.

- How many different ways the words can be arranged in a row?
- How many ways of arrangement that all three letters of “E” are not together?

*Guide: *

**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!)

**Permutation & Combination (Answer)**

- 20
- 14

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