This page reads wave speed from a wavelength and a frequency instead of from field amplitudes. The worked ledger makes the product visible, so a learner can see which measured inputs set the speed and where significant figures would enter outside the clean model.
The same speed check must hold from the wavelength-frequency relation. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Wavelength and frequency close the same speed loop
A training wave with wavelength 3 metres and frequency 2 hertz gives the same speed value.