Question

Реки скорость течения 3 км/ч. Моторная лодка по течению 4 часа проехала столь же большое расстояние, как за 8 часов против течения. Вычисли скорость моторной лодки в стоячей воде! Сколько км резак съехал против течения?

Answer 1

Ответ:

Пошаговое объяснение:

V (теч.р.) = 3км/ч

S (по теч.р.) = S (против теч.р.)

S (по теч.р.) = 4ч * (V(по теч.р.) + V (моторной лодки))

S (против теч.р.) = 8ч * ( V (моторной лодки) - V(по теч.р.))

V(моторной лодки) = х, тогда

4 * (3 + х) = 8 * (х - 3)

12 + 4х = 8х - 24

4х - 8х = -24 - 12

-4х = -36

х = 9км/ч -- V моторной лодки в стоячей воде

S (против теч.р.) = 8 * ( 9 - 3 ) = 48км проплыл против течения воды.

Answer 2

Ответ:9км/ч скорость моторной лодки в стоячей реке.

Пошаговое объяснение:

4# (3 + х) = 8#(х - 3)

12 + 4х = 8х - 24

4х - 8х = -24 - 12

-4х = -36

х = 9км/ч -- V моторной лодки в стоячей воде

Answer 3

#### Problem Analysis We are given the following information: - The speed of the river current is 3 km/h. - A motorboat travels for 4 hours with the current and covers the same distance as it would in 8 hours against the current. We need to find: 1. The speed of the motorboat in still water. 2. The distance the boat traveled against the current. #### Solution Let's assume the speed of the motorboat in still water is **x km/h**. When the motorboat is traveling with the current, its effective speed is the sum of the speed of the boat in still water and the speed of the current. Therefore, the effective speed is **(x + 3) km/h**. When the motorboat is traveling against the current, its effective speed is the difference between the speed of the boat in still water and the speed of the current. Therefore, the effective speed is **(x - 3) km/h**. According to the given information, the motorboat travels for 4 hours with the current and covers the same distance as it would in 8 hours against the current. This means that the distance traveled with the current is equal to the distance traveled against the current. Let's calculate the distances traveled in both cases: - Distance traveled with the current = (speed with the current) * (time with the current) - Distance traveled against the current = (speed against the current) * (time against the current) Since the distances are equal, we can set up the following equation: **(x + 3) * 4 = (x - 3) * 8** Now, let's solve this equation to find the value of **x**. #### Calculation Expanding the equation: 4x + 12 = 8x - 24 Rearranging the terms: 4x - 8x = -24 - 12 -4x = -36 Dividing both sides by -4: x = 9 The speed of the motorboat in still water is **9 km/h**. To find the distance the boat traveled against the current, we can use the formula: Distance = Speed * Time The time against the current is 8 hours, and the speed against the current is (9 - 3) km/h = 6 km/h. Therefore, the distance traveled against the current is: Distance = 6 km/h * 8 hours = 48 km. #### Answer The speed of the motorboat in still water is **9 km/h**. The boat traveled **48 km** against the current.