The average of 10 observations is 40. It was realised later that an observation was misread as 34 in place of 43. Find the correct average.

Question

Question

This question was previously asked in

RRB NTPC Graduate Level CBT-I Official Paper (Held On: 06 Jun, 2025 Shift 2)

Answer 1

Given:

The average of 10 observations = 40

Misread observation = 34 (instead of 43)

Total observations = 10

Formula used:

Corrected Average = (Old Total + Correction) / Number of Observations

Correction = Correct Value - Misread Value

Calculations:

Old Total = Average × Number of Observations

⇒ Old Total = 40 × 10

⇒ Old Total = 400

Correction = 43 - 34

⇒ Correction = 9

Correct Total = Old Total + Correction

⇒ Correct Total = 400 + 9

⇒ Correct Total = 409

Corrected Average = Correct Total / Number of Observations

⇒ Corrected Average = 409 / 10

⇒ Corrected Average = 40.9

∴ The correct answer is option (1).

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