Committee Permutations
1. Problem a: Find the number of committees of 5 members from 8 women and 4 men with at most 2 men.
- "At most 2 men" means 0, 1, or 2 men.
- Total members = 5.
Calculate for each case:
- Case 0 men: Choose 0 men from 4 and 5 women from 8:
$$\binom{4}{0} \times \binom{8}{5} = 1 \times 56 = 56$$
- Case 1 man: Choose 1 man from 4 and 4 women from 8:
$$\binom{4}{1} \times \binom{8}{4} = 4 \times 70 = 280$$
- Case 2 men: Choose 2 men from 4 and 3 women from 8:
$$\binom{4}{2} \times \binom{8}{3} = 6 \times 56 = 336$$
Total committees:
$$56 + 280 + 336 = 672$$
2. Problem b: Write the total number of permutations of a set of $n$ objects arranged in a circle.
- The number of distinct circular permutations of $n$ objects is:
$$ (n-1)! $$
3. Problem c: Eight members sit at a round table. President and vice president must sit together.
- Treat president and vice president as a single unit.
- Then we have 7 units to arrange around the table.
- Number of circular permutations of 7 units:
$$ (7-1)! = 6! = 720 $$
- President and vice president can switch seats within their unit:
$$ 2! = 2 $$
Total arrangements:
$$ 720 \times 2 = 1440 $$
Final answers:
- a) 672 committees
- b) $ (n-1)! $ permutations
- c) 1440 seating arrangements