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Question
The mean of five numbers is 27. If one number is excluded, the mean of the remaining numbers is 25. Find the excluded number.
Solution
The mean of 5 observations = 27
Total sum of 5 observations = 27 × 5 = 135
On excluding an observation, the mean of the remaining 4 observations = 25
⇒ Total of remaining 4 observations = 25 × 4 = 100
⇒ Included observation = Total mean of 5 observations – Total mean of 4 observations
= 135 − 100 = 35
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