Additional Mathematics – Permutations and combinations | e-Consult
Permutations and combinations (1 questions)
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Answer 3
- Choose which letter will be the repeated one: 4 choices.
- Choose the positions for the two repeated letters among the 5 slots: C(5,2) = 10 ways.
- For the remaining three positions, select three distinct letters from the remaining three letters (since one letter is already used twice, three letters remain). The number of ways to arrange these three distinct letters is 3! = 6.
- Multiply the choices: 4 × 10 × 6 = 240.
Thus, there are 240 such codes.