A series of book was published at seven year intervals. When the seventh book…
2024
A series of book was published at seven year intervals. When the seventh book was published the total sum of publication year was 13, 524. First book was published in?
Answer: C. 1911 — Solution: Let the first publication year be n. The seven publication years form an arithmetic sequence: n, n+7, n+14, ..., n+42. Average year = (first +…
- A.
2911
- B.
2005
- C.
1911
- D.
1950
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Correct answer: C
Solution:
Let the first publication year be n. The seven publication years form an arithmetic sequence: n, n+7, n+14, ..., n+42.
Average year = (first + last)/2 = (n + (n + 42))/2 = n + 21.
Total sum = number of terms × average = 7 × (n + 21) = 7n + 147.
Set the sum equal to 13,524 and solve:
7n + 147 = 13,524 ⇒ 7n = 13,377 ⇒ n = 13,377/7 = 1,911.
Answer: 1911
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