so the basic formula for this d = rt
where d is the distance , r is the speed and t is time
Â
3800 – 120t = 520 + 40t ( this is the altitude of each plane are equal)
Solve for t
T = 20.5 min time it takes for the planes to be at the same altitude
Â
3800 – 120(20.5) = 1340 ft
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