Additional Mathematics – Permutations and combinations | e-Consult
Permutations and combinations (1 questions)
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Answer 1
- Calculate the total number of unrestricted arrangements: 6! = 720.
- Count the arrangements where Alpha and Beta are together. Treat the pair as a single unit; then we have 5 units to arrange, giving 5! = 120 arrangements. Within the pair, the two books can be ordered in 2 ways, so the total with the pair together is 120 × 2 = 240.
- Subtract the unwanted arrangements from the total: 720 – 240 = 480.
Therefore, there are 480 permissible arrangements.