How is the miles needed to descend calculated when approaching from 35,000 feet?

The correct method to calculate the miles needed to descend when approaching from 35,000 feet is based on the understanding of how descent rates work in aviation. Specifically, the well-known rule of thumb states that for each 1,000 feet of altitude, an aircraft generally requires around 3 miles to descend safely. This means that if you are at 35,000 feet, you would multiply the number of thousands of feet (in this case, 35) by 3 to determine the distance in miles required for a safe descent.

This approach is based on the typical vertical speed an aircraft descends at, expected airspeed, and the need to ensure a controlled and safe descent profile. As a result, the calculation of feet to descend multiplied by 3 provides a straightforward way to estimate the distance necessary for descent, which aligns with standard practices in aviation.