Answer: 20 km
Step-by-step explanation: Let's assume a trajectory of Ships A (which is moving at 6 km/h) and B (which is moving at 4 km/h)
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A 10 km B
And let's assume that who is going to the right is the positive.
Space (S) = S₀ + vt
For A, its space is SA = 0 + 6t
For B, its space is SB = 10 - 4t
They meet at SA = SB;
6t = 10 - 4t
6t + 4t = 10
10t = 10
t = 1h
If the bird is at 20 km/h and it will fly for 1h, it will travel 20 km