Question

Моторная лодка проплыла 10км против течения реки, затратив 1ч 15мин,затем 21км по точению за 1ч 45мин.Надо найти собственную скорость лодки и скорость течения реки.

Answer 1

S = v * t - формула пути
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1) S = 10 км;    t = 1 ч 15 мин = 1 ч + (15 : 60) ч = 1,25 ч
10 : 1,25 = 8 (км/ч) - скорость лодки против течения реки;
2) S = 21 км;   t = 1 ч 45 мин = 1 ч + (45 : 60) ч = 1,75 ч
21 : 1,75 = 12 (км/ч) - скорость лодки по течению реки;
3) (8 + 12) : 2 = 10 (км/ч) - собственная скорость лодки;
4) (12 - 8) : 2 = 2 (км/ч) - скорость течения реки.
Ответ: 10 км/ч; 2 км/ч.

Проверка:
(10 - 2) * 1,25 = 10 (км) - путь лодки против течения реки
(10 + 2) * 1,75 = 21 (км) - путь лодки по течению реки

Answer 2

Calculation of Boat's Speed and River's Current Speed

To find the boat's speed and the river's current speed, we can use the given information about the distances traveled and the time taken in each scenario.

Let's denote the boat's speed as B and the river's current speed as R.

1. First scenario: The boat traveled 10 km against the current in 1 hour 15 minutes. - Distance: 10 km - Time: 1 hour 15 minutes = 1.25 hours

2. Second scenario: The boat traveled 21 km with the current in 1 hour 45 minutes. - Distance: 21 km - Time: 1 hour 45 minutes = 1.75 hours

Calculating the Boat's Speed

To calculate the boat's speed, we can use the formula:

Boat's Speed = Distance / Time

For the first scenario: - Boat's Speed = 10 km / 1.25 hours = 8 km/h

For the second scenario: - Boat's Speed = 21 km / 1.75 hours = 12 km/h

Therefore, the boat's speed is 8 km/h in the first scenario and 12 km/h in the second scenario.

Calculating the River's Current Speed

To calculate the river's current speed, we can use the formula:

River's Current Speed = (Boat's Speed with Current - Boat's Speed against Current) / 2

Using the boat's speed from the first and second scenarios, we can calculate the river's current speed:

- River's Current Speed = (12 km/h - 8 km/h) / 2 = 2 km/h

Therefore, the river's current speed is 2 km/h.

In summary, the boat's speed is 8 km/h and the river's current speed is 2 km/h.