6класс , сложные , тема: длина окружности , площадь круга . 1 сколько шаров радиусом 2 см войдет в коробку имеющую форму куба с ребром 20 см. 2 радиус колеса машины 37, 5 см . машина едет по шоссе с такой скоростью , что каждую минуту колеса делают 400 оборотов , найдите скорость машины в км/ч ответ этой должен быть такой : 56, 52 км / ч написано сзади ) 3 часы показывают 2 ч 25 мин . найдите градусную меру угла между часовой и минутной стрелками часов. ответ таков : 77, 5 градусов

Решение: 20/4=5 шаров в каждом направлении(длина, ширина, высота)

5*5*5=125 всего шаров. 2) Длина окружности колеса = 2*3,14*37,5 = 235,5 см. В минуту он проходит - 235,5*400 = 94200 см/мин скорость, переводим 942 м * 60  мин = 56520 м/ч = 56, 52 км/ч. 3) 

1 дм² = 100 см²

12 000 см²  и  12 дм²

12 дм² = 12 * 100 = 1 200 см²     ⇒   12 000 см² > 12 дм²

1 км = 1 000 м

12 км  и  1 200 м:

12 км = 12 * 1 000 = 12 000 м    ⇒    12 км > 1 200 м

1 дм³ = 1 000 см³

12 000 см³  и  12 дм³:

12 дм³ = 12 * 1 000 = 12 000 см³    ⇒   12 000 см³ = 12 дм³

1 дм = 100 мм

12 000 мм  и  1 200 дм:

1 200 дм = 1 200 * 100 = 120 000 мм    ⇒    12 000 мм < 1 200 дм

1 т = 1 000 кг;   1 ц = 100 кг

1 т 2 ц  и  1 200 кг:

1 т 2 ц = 1 * 1 000 + 2 * 100 = 1 200 кг   ⇒    1 т 2 ц = 1 200 кг

A rain in which the precipitation is unusually acidic is called an acid rain. It contains high levels of hydrogen ions. Acid rain is caused when sulphur dioxide and nitrogen dioxide emissions react with water molecules in the air and result in producing acids. These chemicals are produced because of natural sources like decay of vegetation, volcanoes and also from manmade sources like emissions from factories and various types of pollution in the atmosphere. When these gases react with water that is present in the air, form into various acidic compositions.
Acid rains are very harmful to the atmosphere. Steel structures like bridges and towers corrode because of the acid. It also results in the peeling of paint from the painted surfaces like buildings. Stone structures get eroded because of the acid in the rain. 
Acid rain shows adverse effects on human health, forests, sources of fresh water like rivers and streams, and on soil affecting different life forms surviving in these mediums. 
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