Question

Баржа в 8:00 вышла из пункта А в пункт В,расположенный в 30 км по реке от пункта А.Пробыв в пункте В 2 час 30 минут,баржа отправилась назад и вернулась в пункт А в 21:00.Определите собственную скорость баржи, если известно, что скорость течения реки 3 км/ч.

Answer 1

30:(х-3)+30:(х+3)=10,5
Ну уравнение составить самое главное, решишь уже сам(а)

Answer 2

Problem Analysis

We are given the following information: - A barge left point A and traveled to point B, which is located 30 km downstream from point A. - The barge stayed at point B for 2 hours and 30 minutes. - The barge then returned to point A and arrived at 21:00. - The river current has a speed of 3 km/h.

We need to determine the speed of the barge.

Solution

To solve this problem, we can use the formula: distance = speed × time.

Let's break down the problem into two parts: the downstream journey from point A to point B, and the upstream journey from point B back to point A.

# Downstream Journey

During the downstream journey, the barge is moving in the same direction as the river current. Therefore, the effective speed of the barge is the sum of its own speed and the speed of the river current.

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

The distance between point A and point B is given as 30 km.

The time taken for the downstream journey can be calculated using the formula: time = distance / speed.

Substituting the values, we have: time = 30 km / (x km/h + 3 km/h).

# Upstream Journey

During the upstream journey, the barge is moving against the river current. Therefore, the effective speed of the barge is the difference between its own speed and the speed of the river current.

The distance between point B and point A is also 30 km.

The time taken for the upstream journey can be calculated using the formula: time = distance / speed.

Substituting the values, we have: time = 30 km / (x km/h - 3 km/h).

# Total Time

The total time taken for the entire round trip is given as 13 hours (from 8:00 to 21:00), which is equal to 13 hours × 60 minutes/hour = 780 minutes.

The total time can be calculated as the sum of the downstream time, the time spent at point B, and the upstream time: total time = downstream time + 150 minutes + upstream time.

# Solving the Equations

We can now set up the equations and solve for the speed of the barge.

From the downstream journey: 30 km / (x km/h + 3 km/h) = downstream time.

From the upstream journey: 30 km / (x km/h - 3 km/h) = upstream time.

From the total time: downstream time + 150 minutes + upstream time = 780 minutes.

Solving these equations will give us the speed of the barge.

Calculation

Let's solve the equations to find the speed of the barge.

From the downstream journey: 30 km / (x km/h + 3 km/h) = downstream time.

From the upstream journey: 30 km / (x km/h - 3 km/h) = upstream time.

From the total time: downstream time + 150 minutes + upstream time = 780 minutes.

Let's solve these equations:

30 km / (x km/h + 3 km/h) = downstream time .

30 km / (x km/h - 3 km/h) = upstream time .

downstream time + 150 minutes + upstream time = 780 minutes.

We can solve these equations to find the value of x, which represents the speed of the barge.