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.
Computer Dreamer Who Invented the Mouse
Douglas C. Engelbart was 25, just engaged to (be MARRied) and
thinking about his future when he had a dream in 1950 that
(would change/has CHANGEd) the world.
He had a good job working at a government aerospace
laboratory in California, but he wanted to do something
(more) with his life, something of value that might last,
even outlive him. Then it came to him. In a single stroke
he (HAd) what might be safely called a complete
vision of the information age.
The angel in his dream spoke to him of technology’s
potential (EXPANDing) human intelligence, and from it he
made out a career that indeed had lasting impact. It led to a
host of inventions that became the basis for the Internet
and the modern personal computer.
In (LATEr) years, one of those inventions was given a
warmhearted name, reminding of a small, furry creature
given to scurrying across flat surfaces: the computer
mouse.
Computing was in its infancy when Dr. Engelbart entered
the field. Computers were ungainly room-size calculating
machines that could (be USEd) by only one person at a
time. Someone would feed them information in stacks of
punched cards and then wait hours for a printout of
answers. Interactive computing was a thing of the future,
or in science fiction. But it was growing in (DR. ENGELBART's)
restless mind.
In his dream, he saw himself (SITting) in front of a large
computer screen full of different symbols. The screen, he
thought, would serve as a display for a workstation that
would organize all the information and communications
for a given project.
Will they go there tomorrow or next month?
Shall we give them the tiger or the lion?