People in a stadium make a wave. Seats in a row are 0.55 m apart…

Step 1. Speed. The wave moves $0.55\ \text{m}$ in $0.05\ \text{s}$. So $v = \dfrac{0.55\ \text{m}}{0.05\ \text{s}} = 11\ \text{m/s}$.

Step 2. One round. $t = \dfrac{640\ \text{m}}{11\ \text{m/s}} = 58.2\ \text{s}$.

Step 3. The people. Nobody moves round the stadium. Each person stands up and sits down in the same seat. Only the pattern travels. The motion of each person is up and down, across the direction of travel, so this is a transverse wave.