ответ:
one wonderful day i went to the forest with my camera.i wanted to see an unusually beautiful animal.and here is i saw that not far from me rustled bushes.i approached and saw a wonderful animal through the trees ! and when i saw him i started the dragon ! he had blue eyes.white scales.he was wonderful ! i tried to catch him on camera.and only i could see it,i was amazed ! and i was finally able to take a picture of him.but clearly caught on camera i could only a month later.i thought i'd show this picture to people.but,i thought that then people would be looking for him and then he would die outside the will. and then the earth will lose such a miracle.
that's how i caught the camera wonderful animal !
решение. 1. ri=2*r; rii=r/2; ri/rii=4; не надо ни о какой площади сечения говорить. два куска проволоки содинили последовательно, получили ri=2*r; два куска той же проволоки соединили параллельно, получили rii=r/2; ну, а теперь раздели первое на второе!
а теперь общий случай: ri=r*n; rii=r/n; ri/rii=n^2; кусок проволоки разрезали на n одинаковых кусков. сначала эти куски соединяют последовательно: ri=r*n; затем соединяют параллельно rii=r/n; ну и дели первое на второе и делай выводы.
