Question

Лодка плыла по течению реки 45 мин,а против течения-30 мин.Всего лодка проплыла 11,7км. Скорость течения реки 1,8км/ч.Найдите собственую скорость лодки

Answer 1

T по теч. Реки =45мин или 0,75ч t против течения=30мин или 0,5ч Пусть V по течению =х+1,8, Vпротив теч =x-1,8 Составим уравнение: 0,75(х+1,8)+0,5(х-1,8)=11,7 0,75х+1,35+0,5х-0,9=11,7 1,25х+0,45=11,7 1,25х=11,7-0,45 1,25х=11,25 х=11,25:1,25 х=9 Ответ: собственная скорость лодки =9км/ч

Answer 2

Problem Analysis

We are given the following information: - The boat takes 45 minutes to travel downstream (with the current) and 30 minutes to travel upstream (against the current). - The total distance traveled by the boat is 11.7 km. - The speed of the river current is 1.8 km/h.

We need to find the speed of the boat.

Solution

Let's assume the speed of the boat is x km/h.

When the boat is traveling downstream, the effective speed is the sum of the boat's speed and the speed of the current. Therefore, the effective speed is (x + 1.8) km/h.

When the boat is traveling upstream, the effective speed is the difference between the boat's speed and the speed of the current. Therefore, the effective speed is (x - 1.8) km/h.

We can use the formula distance = speed × time to calculate the distance traveled in each case.

1. When the boat is traveling downstream, the distance traveled is 11.7 km and the time taken is 45 minutes: - Distance = Speed × Time - 11.7 = (x + 1.8) × (45/60) 2. When the boat is traveling upstream, the distance traveled is 11.7 km and the time taken is 30 minutes: - Distance = Speed × Time - 11.7 = (x - 1.8) × (30/60) Now we can solve these two equations to find the value of x, which represents the speed of the boat.

Calculation

Let's solve the equations:

1. 11.7 = (x + 1.8) × (45/60) - Simplifying, we get: 11.7 = (x + 1.8) × 0.75 - Dividing both sides by 0.75, we get: (x + 1.8) = 11.7 / 0.75 - Solving for x, we get: x + 1.8 = 15.6 - Subtracting 1.8 from both sides, we get: x = 15.6 - 1.8 - Therefore, x = 13.8 km/h.

2. 11.7 = (x - 1.8) × (30/60) - Simplifying, we get: 11.7 = (x - 1.8) × 0.5 - Dividing both sides by 0.5, we get: (x - 1.8) = 11.7 / 0.5 - Solving for x, we get: x - 1.8 = 23.4 - Adding 1.8 to both sides, we get: x = 23.4 + 1.8 - Therefore, x = 25.2 km/h.

Answer

The speed of the boat is 13.8 km/h when traveling downstream and 25.2 km/h when traveling upstream.

Please let me know if I can help you with anything else.

Answer 3

Problem Analysis

We are given the following information: - The boat takes 45 minutes to travel downstream (with the current) and 30 minutes to travel upstream (against the current). - The total distance traveled by the boat is 11.7 km. - The speed of the river current is 1.8 km/h.

We need to find the speed of the boat in still water.

Solution

Let's assume the speed of the boat in still water is x km/h.

When the boat is traveling downstream, its effective speed is the sum of its own speed and the speed of the current. Therefore, the boat's effective speed downstream is (x + 1.8) km/h.

Similarly, when the boat is traveling upstream, its effective speed is the difference between its own speed and the speed of the current. Therefore, the boat's effective speed upstream is (x - 1.8) km/h.

We can use the formula speed = distance / time to calculate the distances traveled in each direction.

Calculations

Let's calculate the distances traveled in each direction:

- Downstream: distance = speed × time = (x + 1.8) × 45 minutes = (x + 1.8) × (45/60) km - Upstream: distance = speed × time = (x - 1.8) × 30 minutes = (x - 1.8) × (30/60) km

The total distance traveled is given as 11.7 km. Therefore, we can write