Since $5, a, b$ have an average of 33, then $\frac{5+a+b}{3}=33$. Multiplying by 3, we obtain $5+a+b=3 \times 33=99$, which means that $a+b=94$. The average of $a$ and $b$ is thus equal to $\frac{a+b}{2}=\frac{94}{2}=47$.