Multiple choice

The average of 10 numbers is 21. If one number is excluded, the average becomes 23. What is the excluded number?

  1. 3

  2. 5

  3. 7

  4. 11
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A Correct answer
Explanation

Sum of 10 numbers = 10 * 21 = 210. Sum of 9 numbers = 9 * 23 = 207. Excluded number = 210 - 207 = 3.

AI explanation

Using the excluded number formula, Excluded Number = (Original Average x Original Count) - (New Average x New Count). The sum of all 10 numbers is 10 x 21 = 210. The sum of the remaining 9 numbers is 9 x 23 = 207. The excluded number is 210 - 207 = 3.

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