Question

7. Собственная скорость теплохода 12 км/час, скорость течения реки 3 км/час. Из пункта А в пункт Б по течению реки теплоход проплыл за 9 часов. Сколько часов он будет плыть обратно?​

Answer 1

Ответ:

15 часов понадобится теплоходу на обратный путь

Пошаговое объяснение:

1) 12+3=15 км/ч скорость теплохода по течению реки

2) 15*9=135 км расстояние между пристанями

3) 12-3=9 км/ч скорость теплохода против течения

4) 135:9=15 часов понадобится теплоходу на обратный путь

Answer 2

Calculation of Return Journey Time

To calculate the time it will take for the boat to return from point B to point A, we need to consider the speed of the boat and the speed of the river current.

Given: - Boat speed: 12 km/h - River current speed: 3 km/h - Time taken to travel from A to B with the river current: 9 hours

To find the return journey time, we can use the concept of relative velocity. The boat's speed against the current will be the difference between its speed and the current speed, while the boat's speed with the current will be the sum of its speed and the current speed.

Let's calculate the boat's speed against the current: Boat's speed against the current = Boat's speed - River current speed = 12 km/h - 3 km/h = 9 km/h

Now, we can calculate the return journey time using the formula: Return journey time = Distance / Boat's speed against the current

Since the distance from point B to point A is the same as the distance from point A to point B, we can use the same distance for the return journey.

Let's assume the distance between point A and point B is D km.

Return journey time = D km / 9 km/h

Therefore, the boat will take D/9 hours to return from point B to point A.

Please note that the exact value of the return journey time cannot be determined without knowing the distance between point A and point B.