Errr...Howard - Desc from FL300 is 30 X 3 = 90. Therefore commence descent from approx 90 miles (plus or minus wind or other considerations).
JT
FL300 / 3 = 100 is closer to a 3 degree profile than doing it the other way. At anyrate, we multiply height by 3 for a descent point (your way) but then transition to multiplying distance by 3 (Howard's way) closer in to the airport
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