Долгота круга ровна 18п см. найдите площадь круга, ограничанным этим кругом

Наверно подразумевается ДЛИНА ОКРУЖНОСТИ = 18 см.
Длина окружности = L= 2*pi*R= 18 см
Отсюда находим R= 18/(2*3.14)= 2.866 см
Используем значение L/2 = pi*R = 9/
Площадь круга S= pi*R^2 = (pi*R)*R =9*2.866 = 25.8 кв.см.
ответ: Площадь круга 25,8 кв.см.

Пусть Х км/ч - собственная скорость лодки ( т е скорость лодки в стоячей воде)
Тогда (Х+3) - скорость по течению
(Х-3) - скорость против течения
35/(Х+3) - время по течению

35/(Х-3) - время против течения

Известно, что на обратный путь лодка затратила на 40 мин меньше
40 мин = 40/60ч = 2/3 ч
Составим уравнение:

35/(х-3) - 35/(Х+3) =2/3

3*35(Х+3) - 3*35(Х-3)=2(х^2-9)

105х + 315 - 105х + 315 = 2х^2 -18

- 2х^2 = - 648
Х^2= 324
Х1,2= корень из 324=18
Х1= 18
Х2= - 18 ( не явл корнем )

ответ : 18 км/ч - скорость лодки в неподвижной воде

1. 1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/3

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/3

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/32) 7/10 + 2 3/5 = 7/10 + 2 6/10 = 2 13/10 = 3 3/10

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/32) 7/10 + 2 3/5 = 7/10 + 2 6/10 = 2 13/10 = 3 3/103) 4 2/5 : 3 3/10 = 22/5 : 33/10 = 22/5 * 10/33 = (2*2)/(1*3) = 4/3 = 1 1/3

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/32) 7/10 + 2 3/5 = 7/10 + 2 6/10 = 2 13/10 = 3 3/103) 4 2/5 : 3 3/10 = 22/5 : 33/10 = 22/5 * 10/33 = (2*2)/(1*3) = 4/3 = 1 1/34) 1 16/17 : 11 = 33/17 * 1/11 = (3*1)/(17*1) = 3/17

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/32) 7/10 + 2 3/5 = 7/10 + 2 6/10 = 2 13/10 = 3 3/103) 4 2/5 : 3 3/10 = 22/5 : 33/10 = 22/5 * 10/33 = (2*2)/(1*3) = 4/3 = 1 1/34) 1 16/17 : 11 = 33/17 * 1/11 = (3*1)/(17*1) = 3/175) 3/17 - 3/17 = 0

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/32) 7/10 + 2 3/5 = 7/10 + 2 6/10 = 2 13/10 = 3 3/103) 4 2/5 : 3 3/10 = 22/5 : 33/10 = 22/5 * 10/33 = (2*2)/(1*3) = 4/3 = 1 1/34) 1 16/17 : 11 = 33/17 * 1/11 = (3*1)/(17*1) = 3/175) 3/17 - 3/17 = 06) 1/3 + 1 1/3 = 1 2/3

1 2/9 : 3 2/3 + 4 2/5 : (7/10 + 2 3/5) - (3/17 - 1 16/17 : 11) = 1 2/31) 1 2/9 : 3 2/3 = 11/9 : 11/3 = 11/9 * 3/11 = 3/9 = 1/32) 7/10 + 2 3/5 = 7/10 + 2 6/10 = 2 13/10 = 3 3/103) 4 2/5 : 3 3/10 = 22/5 : 33/10 = 22/5 * 10/33 = (2*2)/(1*3) = 4/3 = 1 1/34) 1 16/17 : 11 = 33/17 * 1/11 = (3*1)/(17*1) = 3/175) 3/17 - 3/17 = 06) 1/3 + 1 1/3 = 1 2/37) 1 2/3 - 0 = 1 2/3

2. 5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/3

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/57

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/572) 10/57 - 10/57 = 0

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/572) 10/57 - 10/57 = 03) 2 3/4 : 4 8/9 = 11/4 : 44/9 = 11/4 * 9/44 = (1*9)/(4*4) = 9/16

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/572) 10/57 - 10/57 = 03) 2 3/4 : 4 8/9 = 11/4 : 44/9 = 11/4 * 9/44 = (1*9)/(4*4) = 9/164) 9/16 * 2 2/3 = 9/16 * 8/3 = (3*1)/(2*1) = 3/2 = 1 1/2

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/572) 10/57 - 10/57 = 03) 2 3/4 : 4 8/9 = 11/4 : 44/9 = 11/4 * 9/44 = (1*9)/(4*4) = 9/164) 9/16 * 2 2/3 = 9/16 * 8/3 = (3*1)/(2*1) = 3/2 = 1 1/25) 5/6 + 1 1/2 = 5/6 + 1 3/6 = 1 8/6 = 2 2/6 = 2 1/3

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/572) 10/57 - 10/57 = 03) 2 3/4 : 4 8/9 = 11/4 : 44/9 = 11/4 * 9/44 = (1*9)/(4*4) = 9/164) 9/16 * 2 2/3 = 9/16 * 8/3 = (3*1)/(2*1) = 3/2 = 1 1/25) 5/6 + 1 1/2 = 5/6 + 1 3/6 = 1 8/6 = 2 2/6 = 2 1/36) 2 1/3 - 1 2/3 = 1 4/3 - 1 2/3 = 2/3

5/6 + 2 3/4 : 4 8/9 * 2 2/3 - 1 2/3 + (5/38 * 1 1/3 - 10/57) = 2/31) 5/38 * 1 1/3= 5/38 * 4/3 = (5*2)/(19*3) = 10/572) 10/57 - 10/57 = 03) 2 3/4 : 4 8/9 = 11/4 : 44/9 = 11/4 * 9/44 = (1*9)/(4*4) = 9/164) 9/16 * 2 2/3 = 9/16 * 8/3 = (3*1)/(2*1) = 3/2 = 1 1/25) 5/6 + 1 1/2 = 5/6 + 1 3/6 = 1 8/6 = 2 2/6 = 2 1/36) 2 1/3 - 1 2/3 = 1 4/3 - 1 2/3 = 2/37) 2/3 + 0 = 2/3