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Railways PYQCBT 1 2016

RRB NTPC · Question 53

The mean of 20 observation is 19. One more observation is included and the new mean becomes 20. The 21st observation is: A. 20 B. 30 C. 40 D. 42

  1. C

  2. D

  3. B

  4. A

Show answer & explanation

Answer: (A) C

Explanation

Total of 20 observations = 20 × 19 = 380. Total of 21 observations = 21 × 20 = 420. The 21st observation = 420 − 380 = 40.