The mean of 5 numbers is 20. If one number is excluded, mean of the remaining numbers becomes 23. Find the excluded number.
Solution:
The mean of 5 numbers = 20
So, the total sum of the numbers = 20×5 = 100
After excluding one number,
The mean of the remaining 4 numbers = 23
So, the total sum of these numbers = 23×4 = 92
Hence, the excluded number is = 100 – 92 = 8.
The mean of 25 observations is 27. If one observation is included, the mean still remains 27. Find the included observation.
Solution:
The mean of 25 observations is 27.
So, the total sum of all the 25 observations = 27×25 = 675
After one observation is included,
Now the mean of 26 (25 + 1) numbers = 27
So, the total sum of all the 26 observations = 27×26 = 702
Hence, the included observation = 702 – 675 = 27
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