mark and his friend are thirteen years old.and they are very sporty. they often go to the gym - at least three timesa week. mark does exercises to make his arms strong.he can t walk because of a car accident, so he goes everywhere in wheelchair. but it doesn t stop him doing the things that boys our age want to do.
Ответ дал: Гость
площадь круга вычисляется по формуле:
s = πr²
по условию, радиус стал равен r/2. подставим это выражение в формулу:
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