Предмет: Алгебра, автор: aleksandrgerinp6ytbi

Как называется способ решения этого примера . Пожалуйста помогите!

Приложения:

MizoriesKun: решение способом подстановки

Ответы

Автор ответа: sokisok

способ решения: система

Автор ответа: trifonoffdanya

этот способ называется:
система

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Read this passage and answer the questions that follow.

Today we have many ways to tell time. Watches, clocks, cell phones, and computers all tell the time. This passage is about the history of different ways of telling time and its importance.

What Time Is It?

Believe it or not, there was a time when humans were not concerned with the exact time of day. There were no clocks or watches. Instead, their daily activities were guided by the rising and the setting of the sun. As societies became more organized, the idea of "time" grew in importance.

Among the earliest initiatives to mark time was the shadow clock, which used the sun’s light to cast a shadow on a specially-marked surface. This led to the sundial. In Egypt, there is a shadow clock that dates back to the 8th century. This timepiece was useful, but it could not tell time when there was no sun. It was clear that some other form of timekeeping had to be developed.

There were several devices created to supplement or replace sundials. One such device was the notched candle, which let people calculate the time by looking at how far down the candle had burned. The Chinese came up with a somewhat similar contrivance by burning a knotted rope.

Some ancient people used a water clock known as a "clepsydra." The clepsydra

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These early efforts to tell time served a need, but none of them offered a precise measure of time. With the introduction of the first weight-driven clock in 1286, the technology to develop more accurate means of keeping time had begun. By the mid-1300s, an astronomer and physician named Giovanni de’ Dondi completed an early astronomical clock. He produced a seven-sided clock whose dials showed the sun, the moon, and the known planets. In addition to the 24 hours, it showed the times of sunrise and sunset, religious holidays, and the cycles of the moon. His "astrarium" was a remarkable advance over previous timepieces. However, it wasn’t until 300 years later, in 1650, that the first clock using two hands to tell the time was made.

Through the next centuries, numerous changes took place in the clock industry. Some clockmakers produced clocks that were works of art with beautiful gilt figures surrounding the clock faces. Others refined the size all the way down from the dimensions of huge clocks in bell towers to those of today’s wristwatches. Power sources to control the clock mechanisms changed, too – from coil springs to quartz.

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Even for a society obsessed with schedules and doing things or being places promptly, the atomic clock may even be more than we need just to be on time!

1. Thousands of years ago, people would base their activities upon the

A. sound of the rooster.

B. amount of work to be done.

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D. rising and setting of the sun.

2. The author attempts to

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B. tell the story of how the atomic clock was built.

C. challenge readers to find a better way to tell time.

D. describe different ways people have told time.

3. What was the oldest form of timekeeping?

A. clepsydra

B. atomic clock

C. astrarium

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4. How did the weight-driven clock change the science of telling time?

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B. It allowed timepieces to become hand-held.

C. It marked the beginning of new technology.

D. It marked the end of using the sun to tell time.

5. The atomic clock is

A. not built yet.

B. dangerous.

C. outdated.

D. precise.

6. What was the biggest advance in timekeeping?

A. the sundial

B. the atomic clock

C. global positioning systems

D. the wristwatch

[7 points]

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