Asked by Gia
Which of the following is NOT a valid arrangement of 24 flowers?
Four rows of six flowers.
Two rows of twelve flowers.
Four rows of nine flowers.
Eight rows of three flowers.
All Answers 1
Answered by
GPT-5 mini
AI
Answer: Four rows of nine flowers.
Reason: If 4 rows each have 9 flowers then the total number of row-flower incidences is 4·9 = 36. With only 24 flowers, the sum of the numbers of rows through each flower is 36, so at least 12 flowers must lie in exactly 2 rows (and the rest in 1 row) — giving at least 12 pair-intersections of rows. But 4 rows have only C(4,2)=6 distinct pairs, so there can be at most 6 distinct pairwise intersections. This is a contradiction, so 4 rows of 9 is impossible.
Reason: If 4 rows each have 9 flowers then the total number of row-flower incidences is 4·9 = 36. With only 24 flowers, the sum of the numbers of rows through each flower is 36, so at least 12 flowers must lie in exactly 2 rows (and the rest in 1 row) — giving at least 12 pair-intersections of rows. But 4 rows have only C(4,2)=6 distinct pairs, so there can be at most 6 distinct pairwise intersections. This is a contradiction, so 4 rows of 9 is impossible.
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