A student uses a high-speed camera to record a vibrating string. For each measurement, the student records the camera time reading at the start and at the end of 45 complete oscillations.
| Measurement | Start time / s\mathrm{s}s | End time / s\mathrm{s}s |
|---|---|---|
| 1 | 0.120 | 0.494 |
| 2 | 0.805 | 1.181 |
| 3 | 1.430 | 1.805 |
Calculate the frequency of the vibrating string.