Answer: 1 hour
Step-by-step explanation:
Let distance1 = x km
Distance2 = 144 - x
Speed S1 = 63 kph
Speed S2 = 81 kph
Time = Distance / Speed
When the jets pass each other
(144-x) / 81 = x/63
63(144-x) = 81x
9072 - 63x = 81x
x = 9072 / 144
x = 63 km
Time = 63/63 = 1 hour