What is the arithmetic mean (average) of the first 10 whole numbers?

The correct answer is Option (4) → 4.5

The whole numbers start from 0, so the first 10 whole numbers are 0, 1, 2, ..., 9. For numbers in equal steps, the average is the average of the first and the last.

• First 10 whole numbers: 0 to 9

• Sum \(=0+1+2+\dots+9=45\)

• Average \(\displaystyle =\frac{45}{10}=4.5\), the same as \(\displaystyle \frac{0+9}{2}\)

The mean is 4.5. Taking the natural numbers 1 to 10 instead would give 5.5, which is Option (3).