Note: We are not 100% sure of the exact nature of this question due to the quality of feedback received, so do expect some differences in the exam. Please let us know in the comments if you see it in the real exam, thank you!

The required rate of descent to maintain a particular glidepath (usually 3° where possible) is based solely on the aircraft's groundspeed. For instance, the calculation to determine the required rate of descent is ground speed multiplied by descent gradient (in percent). Therefore, for a 3° glidepath, the gradient is 5%, and the required rate of descent is 5 times the groundspeed. For example, an aircraft on the approach at 150 kt GS should descend at 750 ft/min to maintain a 3° descent angle.

In still air conditions, the ground speed is equal to the TAS (True Airspeed), so this can be used instead.