  At scattered places of his notebooks, Ramanujan recorded over 30 values of
singular moduli $\alpha_n$. All those results were proved by Berndt et. al by
employing Weber-Ramanujan's class invariants. In this paper, we initiate to
derive the explicit evaluations formula for $\alpha_{9n}$ and $\alpha_{n/9}$ by
involving class invariant. For this purpose, we establish several new $P-Q$
mixed modular equations involving theta-functions. Further application of these
modular equations, we derive a new formula to explicit evaluation of Ramanujan-
Selberg continued fraction.
