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Question
The mean of nine numbers is 77. If one more number is added to it then the mean increases by 5. Find the number added in the data.
Solution
We have, the mean of nine numbers is 77.
The sum of nine numbers = 77 × 9 = 693.
The new mean when one more number is added to it = 77 + 5 = 82.
The sum of ten numbers = 82 × 10 = 820.
So, the number added in the data = 820 − 693 = 127.
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