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The crew of an 8-member rowing team is t...

The crew of an 8-member rowing team is to be chosen from 12 men (`M_1, M_2, ...., M_(12)`) and 8 women `(W_1, W_2, ...., W_8)`. There have to be 4 people on each side with at least one woman on each side. Further it is also known that on the right side of the boat (while going forward) `W_1` and `M_1` must be selected while on the left side of the boat `M_2, M_3` and M10 must be selected. What is the number of ways in which the rowing team can be arranged?

A

`1368 xx 4! xx 4!`

B

`1274 xx 4! xx 4!`

C

`1120 xx 4 ! xx 4!`

D

`728 xx 4! xx 4!`

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The correct Answer is:
To solve the problem of arranging the rowing team, we will break it down step by step. ### Step 1: Understand the Composition of the Team We have a total of 12 men and 8 women. We need to form a rowing team of 8 members, with 4 members on each side of the boat. Each side must have at least one woman. ### Step 2: Assign Fixed Members We know that: - On the right side, `W_1` (a woman) and `M_1` (a man) must be selected. - On the left side, `M_2`, `M_3`, and `M_10` (all men) must be selected. ### Step 3: Determine Remaining Members After assigning the fixed members: - **Right Side**: We have already selected `W_1` and `M_1`, leaving us to select 2 more members. - **Left Side**: We have already selected `M_2`, `M_3`, and `M_10`, leaving us to select 1 more member. ### Step 4: Count Available Members - Remaining members after selecting the fixed ones: - Men left: 12 total - 4 selected = 8 men left (M_4, M_5, M_6, M_7, M_8, M_9, M_11, M_12) - Women left: 8 total - 1 selected = 7 women left (W_2, W_3, W_4, W_5, W_6, W_7, W_8) ### Step 5: Select Members for Each Side 1. **Right Side Selection**: - We need to select 2 more members from the remaining 8 men and 7 women, ensuring at least one woman is included. - We can choose: - 1 woman and 1 man, or - 2 women 2. **Left Side Selection**: - We need to select 1 more member from the remaining 8 men and 7 women, ensuring at least one woman is included. - We can choose: - 1 woman, or - 1 man (but since we need at least one woman on this side, we will select a woman). ### Step 6: Calculate Combinations 1. **Right Side Combinations**: - **Case 1**: 1 woman and 1 man - Choose 1 woman from 7: \( \binom{7}{1} = 7 \) - Choose 1 man from 8: \( \binom{8}{1} = 8 \) - Total for this case: \( 7 \times 8 = 56 \) - **Case 2**: 2 women - Choose 2 women from 7: \( \binom{7}{2} = 21 \) - Total for this case: 21 - Total combinations for the right side: \( 56 + 21 = 77 \) 2. **Left Side Combinations**: - We need to choose 1 woman from the remaining 6 women (since `W_1` is already on the right side): - Choose 1 woman from 6: \( \binom{6}{1} = 6 \) ### Step 7: Calculate Arrangements - The arrangements for each side: - Right Side: 4 members can be arranged in \( 4! = 24 \) ways. - Left Side: 4 members can be arranged in \( 4! = 24 \) ways. ### Step 8: Total Combinations The total number of ways to arrange the rowing team is given by: \[ \text{Total Ways} = (\text{Ways to choose for Right Side}) \times (\text{Ways to choose for Left Side}) \times (\text{Arrangements for Right Side}) \times (\text{Arrangements for Left Side}) \] \[ = (77) \times (6) \times (24) \times (24) \] ### Step 9: Final Calculation Calculating the total: \[ = 77 \times 6 \times 24 \times 24 = 77 \times 6 \times 576 = 77 \times 3456 = 265632 \] Thus, the total number of ways to arrange the rowing team is **265632**.
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