A club with x members is organized into tour committees such that(a)ea...
My thought is option BB and x=6x=6. Please somebody tell me am I right or wrong?
Let the committees be A1,A2,A3,A4A1,A2,A3,A4 then |A1∪A2∪A3∪A4|=n|A1∪A2∪A3∪A4|=n. There are (42)=6(42)=6 pairwise intersections each of size 11and each intersection of triples must be empty since if not some member would belong to 33committees, a contradiction. If we make a 4×n4×n table where rows are committees and columns are members and mark a 11 whenever member xjxj belongs to committee AiAi we notice that the ithith row sum is |Ai||Ai| and the jthjthcolumn sum is 22 (since each member belongs to exactly 22 committees) so equating row and column sums we get ∑4i=1|Ai|=2n.∑i=14|Ai|=2n.
Putting this information together and using the inclusion-exclusion formula we get n=6
A club with x members is organized into tour committees such that(a)ea...
Explanation:
Given Conditions:
- Each member is in exactly two committees.
- Any two committees have exactly one member in common.
Reasoning:
- Let's assume there are 'x' members in the club.
- Each member is in exactly two committees, which means there are a total of 2x committee memberships.
- Since any two committees have exactly one member in common, each member is counted twice in the total committee memberships.
- Therefore, the total committee memberships must equal 2x.
Analysis:
- The total number of committee memberships is equal to the sum of the sizes of all committees.
- Let's denote the size of each committee as 'y'.
- The total number of committee memberships is also equal to the total number of committee-member pairs, which is x*y.
- Therefore, 2x = x*y.
Conclusion:
- Solving the equation 2x = x*y gives us y = 2.
- This implies that each committee has 2 members.
- Since each member is in exactly two committees, the total number of members x must be even.
- The only even number between 4 and 8 is 4, so the only possible value for x is 4.
- Hence, the correct answer is that x has exactly one value between 4 and 8.