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.
ghhWhich use(s) of do so is/are natural?
I need to speak to John. I’ll try to do so tomorrow.
Ann's been to Patagonia, and I’d love to do so.
I think you’re wrong, and I've always done so.
One of these is wrong. Which?
Do you ever have time to go to London?
Have you ever got time to go to London?
Do you have time to go to London this weekend?
Have you got time to go to London this weekend?
What does this sentence mean? I had my application form checked by the secretary.
I got the secretary to check my application form.
The secretary took my application form and checked it
Both of the above meanings are possible.
Which of these uses is right?
She can win the race next month if she really tries.
I can speak French well in another three months.
Объяснение: