Find the mean of the first seven odd prime numbers.

First seven odd prime numbers = 3, 5, 7, 11, 13, 17, 19.

Mean (M) = $\dfrac{\text{Sum of first seven odd prime nos.}}{\text{No. of prime nos.}}$

Sum of first seven odd prime numbers = 3 + 5 + 7 + 11 + 13 + 17 + 19 = 75.

$M = \dfrac{75}{7} \\[1em] = 10\dfrac{5}{7}.$

Hence, the mean of the first seven odd prime numbers = $10\dfrac{5}{7}$.