What is the formula to calculate descent gradient?

The formula for calculating descent gradient is derived from the relationship between the altitude change and the horizontal distance over which that change occurs. The correct formula, which is represented here, states that the altitude to lose (in feet) divided by the distance (in nautical miles) gives you the descent gradient in feet per nautical mile.

Using this approach, if you have, for example, an altitude of 3,000 feet that needs to be lost over a horizontal distance of 10 nautical miles, you would divide 3,000 by 10, resulting in a descent gradient of 300 feet per nautical mile. This measurement is crucial for pilots when planning descents, as it helps them maintain a proper profile to arrive at their destination safely and efficiently.

In contrast, the other formula options provided do not accurately represent the calculation of descent gradient. For example, one implies that the distance should be divided by the altitude to lose, which flips the required relationship and would yield an incorrect understanding of how steep the descent is. Another option incorrectly uses multiplication instead of division, failing to reflect the correct relationship needed for calculating descent gradient. Finally, one option calculates descent in feet per minute based on time, which relates to vertical speed but does not directly apply to the