Answer:
0.63 m/s
Step-by-step explanation:
Given that,
Mass of a child = 39 kg
The mass of a boat =64 kg
The child throws a 4.8 kg package horizontally from the boat at a velocity of +13.7 m/s.
We need to find the velocity of the boat after the scenario. The momentum of the system will remain conserved. So,
+ ( + ) = 0

So, the velocity of the boat after this is 0.63 m/s.