The average of first ten prime numbers which are odd is

The first prime number is $2$, which is even. All other prime numbers are odd.
Therefore, the first ten odd prime numbers are:
$3,5,7,11,13,17,19,23,29,\text{ and }31$.

To find their average, we first find the sum of these ten numbers:

$$\text{Sum}=3+5+7+11+13+17+19+23+29+31=158$$

Now, we compute the average:

$$\text{Average}=\frac{\text{Sum}}{\text{Total count}}=\frac{158}{10}=15.8$$