Answer:
Vr = 20 [km/h]
Explanation:
In order to solve this problem, we have to add the relative velocities. We must remember that velocity is a vector, therefore it has magnitude and direction. We will take the sea as the reference measurement level.
Let's take the direction of the ship as positive. Therefore the boy moves in the opposite direction (Negative) to the reference level (the sea).
![V_{r}=30-10\\V_{r}=20 [km/h]](https://tex.z-dn.net/?f=V_%7Br%7D%3D30-10%5C%5CV_%7Br%7D%3D20%20%5Bkm%2Fh%5D)
Early hypotheses were not based on observations.
Early hypotheses were not tested by experimentation.
Early hypotheses were formed from scientific questions.
Early hypotheses were influenced by creative thinking
Answer:

Explanation:
As we know by radioactivity law

so here we will have


now we will have


now we also know that



im a bit confused on what the question is:(
if its just asking for the total number of km traveled it would be 21 km
<span>Igneous rocks which form by the crystallization of magma at a depth within the Earth are called intrusive rocks. Intrusive rocks are characterized by large crystal sizes, i.e., their visual appearance shows individual crystals interlocked together to form the rock mass. hope that helped</span>