Hello
Sorry for my English, I'm writing through a translator.
the solution algorithm seems to have understood, hopefully correctly. Find the area of the base of the cylinder -> find the area of the triangle AOB -> the area of the large triangle - AOB*2 -> subtract the area of the large triangle from the area of the circle and get the area of the segment with water -> the area of the volume is equal - multiply the area of the segment with water by the length of the cylinder (we find from the volume of the cylinder and the area of the base) - the answer is far from the result in the example. I have been working on this task for the second day. I can't understand, do I have the wrong algorithm or calculations?

thank you, your comment broke my wall of misunderstanding