The average number of visitors to a library in the first 4 days of a week was…
2024
The average number of visitors to a library in the first 4 days of a week was 58. The average for the 2nd, 3rd, 4th and 5th days was 60. If the number of visitors on the 1st and 5th days were in the ratio 7 ∶ 8 then what is the number of visitors on the 5th day of the library?
Answer: B. 64 — Solution: Let the number of visitors on days 1 to 5 be a, b, c, d, e respectively. (a + b + c + d)/4 = 58 ⇒ a + b + c + d = 232. (b + c + d + e)/4 = 60 ⇒ b +…
- A.
18
- B.
64
- C.
58
- D.
56
Attempted by 31 students.
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Correct answer: B
Solution:
Let the number of visitors on days 1 to 5 be a, b, c, d, e respectively.
(a + b + c + d)/4 = 58 ⇒ a + b + c + d = 232.
(b + c + d + e)/4 = 60 ⇒ b + c + d + e = 240.
Subtract the two sums: (b + c + d + e) − (a + b + c + d) = 240 − 232 ⇒ e − a = 8.
Given e : a = 8 : 7, set e = 8m and a = 7m. Then 8m − 7m = 8 ⇒ m = 8, so e = 8 × 8 = 64.
Therefore the number of visitors on the fifth day is 64.