Answer:
The time the pilots have to take evasive action is approximately 36.699 seconds
Step-by-step explanation:
The direction of the planes = Towards each other
The speed of each plane, v₁, v₂ = 721 km/h
The initial distance between the two planes, d = 14.7 km
The relative velocity of the two planes, v = v₁ + v₂
v = 721 km/h + 721 km/h = 1,442 km/h
The time it will take the planes to meet, t = d/v
∴ t = 14.7 km/(1,442 km/h) = (21/2,060) h × 60 min/hr × 60 s/min ≈ 36.699 s
The time it will take the planes to meet = The time the pilots have to take evasive action, t ≈ 36.699 seconds.