The arithmetic mean of the observations 28, 31, 40, 63, 57, 37, 34, 70 and 99 is:

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RRB NTPC Graduate Level CBT-I Official Paper (Held On: 06 Jun, 2025 Shift 1)
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  1. 50
  2. 55
  3. 41
  4. 51

Answer (Detailed Solution Below)

Option 4 : 51
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Detailed Solution

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Given:

Observations = 28, 31, 40, 63, 57, 37, 34, 70, 99

Formula used:

Arithmetic Mean (AM) = (Sum of Observations) / (Number of Observations)

Calculation:

Sum of Observations = 28 + 31 + 40 + 63 + 57 + 37 + 34 + 70 + 99

⇒ Sum = 459

Number of Observations = 9

⇒ AM = 459 / 9

⇒ AM = 51

∴ The correct answer is option (4).

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