The average of first 10 even numbers is___________?
Correct answer: D. 11
- A. 18
- B. 22
- C. 9
- D. 11
Explanation
The first 10 even numbers are 2, 4, ..., 20. Since they form an arithmetic sequence, their average is (first number + last number) / 2 = (2 + 20) / 2 = 11. The likely mistake is choosing 22, the sum of the first and last terms, without dividing by 2.
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About Averages
An average represents the total of a set of values divided by the number of values, and a weighted average gives different importance to different groups. Problems involve missing values, combined averages, replacement of observations, and changes in the average, so the total and count must be tracked separately.
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