Counting and logic (contest style)

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Learn it Count arrangements with factorials ($n! = n \times (n - 1) \times \dots \times 1$), divide out repeated letters, and divide by the order of a group when order doesn't matter.

Example: How many arrangements of the letters in LEVEL?

5 letters: $5! = 120$.
L repeats twice and E twice: divide by $2! \times 2! = 4$.
$120 \div 4 = 30$.

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