The question in the book says:

Question

A wave has a wavelength of 2mm and a frequency of 3 Hz. At what speed does the wave travel?

I know the answer is 6, because the formula is Speed= Wavelength X Frequency, but I don't know how to write the final answer, it's going to be 6??

Can you help me out, I just don't know how to label the answer.

Answer 1

c = 2mm x 3(1/sec)
c = 6 mm/sec
The old name for frequency was cycles/sec.
The new name is Herz and that stands for cycles/sec.
Therefore, wavelength x cycle/sec
2 mm x 3 cycles/sec = 6 mm/sec.