Interesting logic puzzles at interviews

Good afternoon, Khabrovsk!

Interview, especially if you did not pass it :), the thing is not very pleasant. But my dad, a mathematics teacher, often said that an exam is not only a way to assess knowledge, but also the most effective teaching method. It is on the exam (in this case, the interview) that a person is more than ever motivated and his brain works at 100%.

In addition, very interesting logical puzzles are sometimes asked at the interview. That's what I want to write about.

So, the most interesting tasks that I was asked at the interview:

Task 1: About the pool, boat and kettlebell.

There is a small pool. A boat floats in it. The current water level is marked on the pool wall.
There is also a cast-iron kettlebell. In which case the water level in the pool rises more: if you lower the weight in the water, or if you lower the weight in the boat?

Problem 2: About Bickford Cords

There are two Bickford cords and a lighter. Cords may burn unevenly. The only thing that is known about them is that each of them will burn for exactly an hour. How to use these items to detect 45 minutes?

Task 3: About a rock and a rope.

A vertical rock 100 meters high. At the top, a hook is hammered for which you can tie a rope. Right under this hook at a height of 50 meters there is a small platform on which you can stand and another hook. At the top of the cliff is a climber. He has 75 meters of rope and a knife to cut it. How can a climber go down a cliff? The length of the rope spent on the nodes is neglected.

Task 4: About the planet and the special points

Are there points on the planet Earth (if there is, then where they are) that satisfy the following condition: If you go from the point 100 km to the north, then 100 km to the east, and then 100 km to the south, you will find yourself at the starting point.

Two of these problems I found on the Internet. A little differently formulated.
I did not find two. Maybe I was looking badly.
Write your answers in comments.
And most importantly, write your interesting puzzles, and links to resources where you can find them.