This question was previously asked in

MP Sub Engg Official Civil Paper Held on 9th July 2017 - Shift 1

Option 2 : 65.7

RRC Group D Full Mock Test

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**Given:**

Mean of 60 observation = 66

Error = 24 was wrongly taken as 42

**Concept used:**

Mean = Total sum/Total number

**Calculations:**

Total sum of 60 observations = 66 × 60 = 3960

Correct sum of 60 observations = 3960 – 42 + 24 = 3942

The correct mean = 3942/60 = 65.7

**∴ The correct mean is 65.7**