Here's how to calculate the speed of a wave:

Formula:

Speed (v) = Wavelength (λ) × Frequency (f)

Given:

* Wavelength (λ) = 4 cm

* Frequency (f) = 8 Hz

Calculation:

v = 4 cm × 8 Hz = 32 cm/s

Answer: The speed of the wave is 32 cm/s.