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Railways PYQCBT 1 2016

RRB NTPC · Question 36

The mean of 7 observations is 18. Another observation is included and the new mean becomes 18.5. The 8th observation is: A. 20 B. 21 C. 22 D. 23

  1. D

  2. A

  3. C

  4. B

Show answer & explanation

Answer: (C) C

Explanation

Sum of 7 = 7 × 18 = 126; sum of 8 = 8 × 18.5 = 148. The 8th observation = 148 − 126 = 22.