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Question
Mean of 10 observations (numbers) is 20. If one number is included, the mean becomes 21, the included number is ______.
Options
431
31
231
131
MCQ
Fill in the Blanks
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Solution
Mean of 10 observations (numbers) is 20. If one number is included, the mean becomes 21, the included number is 31.
Explanation:
The sum of the initial 10 observations is 10 × 20 = 200. When one number is included, the total count becomes 11 with a mean of 21, giving a new sum of 11 × 21 = 231, so the included number is 231 − 200 = 31.
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