Given the wavefunction (in SI units) for a wave to be $ψ_{(x,t)}=10^3 sin \, \pi(3×10^6 x - 9×10^{14} t)$ The speed of the wave is 

3 × 10⁸ ms⁻¹

$ψ_{(x,t)}=10^3 sin \, \pi(3×10^6 x - 9×10^{14} t)$

$=10^3 sin 3 × 10^6 \pi ( x - 3 × 10^8 t)$

Comparing it with the relation

$ψ_{(x,t)}=a sin \frac{2\pi}{λ}(x - ct); $ We note that 

$ c = 3 × 10^8 ms^{-1}$