The average of 11 observations is 72. If average of first 6 observations is 70…
2024
The average of 11 observations is 72. If average of first 6 observations is 70 and that of last 6 observations is 71, then the 6th observation is:
- A.
51
- B.
54
- C.
55
- D.
56
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Correct answer: B
Solution: Use the sums implied by the averages to find the sixth observation.
Total sum of 11 observations = 72 × 11 = 792.
Sum of the first 6 observations = 70 × 6 = 420.
Sum of the last 6 observations = 71 × 6 = 426.
The 6th observation is included in both the first-6 and last-6 sums, so
6th observation = (sum of first 6) + (sum of last 6) − (sum of all 11) = 420 + 426 − 792 = 54.
Answer: 54