Kazan is the capital city of the Republic of Tatarstan. It is also one of the most exciting cities I have ever seen. Last year we visited Kazan with our school teachers and classmates. It was an informative trip, as we saw lots of historic, natural and architectural sights. Our guide was an elderly woman who had a lot to tell. In local language Kazan means “a pot”, which is true as it resembles a hollow or boiler. The city has a favourable geographic position. It is situated near the Volga River which helped to develop trading relations from ancient times. According to historians the city is one thousand years or even older. In the middle of the 16th century it became the part of the Russian empire and the population constantly grew since then. At the moment Kazan shows population over a million people. It features a well-developed chemical and aviation industry, sports and cultural fields. Perhaps, the most popular sport in the city is football. Cultural background is also on good level. You can find the Academic Opera, the Museum of Natural History and other culturally interesting establishments there. All the guests of the city are offered to visit the Kremlin, which is a complex of outstanding monuments. For students Kazan is one of the friendliest cities. It features dozens of educational institutions where you can find the highest level of teaching. It is especially true about the Federal University or Medical University.
Стрелка движется по схеме: "вверх"-"вправо"-"вниз"-"влево"-"вверх". Переход из состояния в соседнее состояние длится 15 секунд. В начальный момент времени стрелка была в положении "вверх". для перехода в положение "влево" ей нужно пройти две позиции "вправо" и "вниз". То есть положение "влево" - третья позиция, всего 3·15с=45с. Аналогично, при переходе из состояния "влево" состояние "вниз" является третьим по счету - это еще 45с. При переходе из состояния "вниз" состояние "вверх" является вторым по счету - это 30с. Два подряд идущих состояния "вверх", при условии, что они были замечены в разные моменты времени, означают, что между их фиксацией стрелка хотя бы один полный круг, то есть на это понадобилось минимум 60с. Итого: 45с+45с+30с+60с=180с=3мин ответ: 3 минуты
