What is the average of the first 15 even natural numbers?

8Correct answerYour answer15Correct answerYour answer16Correct answerYour answer30Correct answerYour answer

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CorrectNot quiteAnswer C

Correct answer: C

The first 15 even numbers are 2, 4, …, 30.
In an evenly spaced list, average = $\frac{\text{first} + \text{last}}{2} = \frac{2 + 30}{2} = 16$ .

Worth noting

Shortcut: average of the first n even numbers = $n + 1$ . 8 is the average of the first 15 natural numbers.

Ten questions from Averages, at your own pace.

Explanation