Question

Теплоход проходит расстояние равное 80 км по течению 4 часа против течения 5 часов. найти скорость течения реки.

Answer 1

Первое действие 80делим4=20
второе действие 20делим5=4

Answer 2

1)80/4=20. 2)80/5=16. 3)20-16=4-скорость течения

Answer 3

Problem Analysis

We are given that a boat travels a distance of 80 km in 4 hours with the current and in 5 hours against the current. We need to find the speed of the river's current.

Solution

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

When the boat is traveling with the current, the effective speed of the boat is the sum of the speed of the boat in still water and the speed of the current. So, the effective speed is (x + y) km/h.

When the boat is traveling against the current, the effective speed of the boat is the difference between the speed of the boat in still water and the speed of the current. So, the effective speed is (x - y) km/h.

We can use the formula speed = distance / time to calculate the speed.

From the given information, we have the following equations:

1. When traveling with the current: (x + y) = 80 / 4 2. When traveling against the current: (x - y) = 80 / 5

We can solve these two equations to find the values of x and y.

Calculation

Let's solve the equations:

1. (x + y) = 80 / 4 - Simplifying, we get: x + y = 20 2. (x - y) = 80 / 5 - Simplifying, we get: x - y = 16 Now, we can solve these two equations simultaneously to find the values of x and y.

Adding equation 1 and equation 2, we get:

(x + y) + (x - y) = 20 + 16

Simplifying, we get:

2x = 36

Dividing both sides by 2, we get:

x = 18

Substituting the value of x in equation 1, we get:

18 + y = 20

Simplifying, we get:

y = 2

Answer

The speed of the river's current is 2 km/h.

Explanation

The boat travels at a speed of 18 km/h in still water, and the river's current is flowing at a speed of 2 km/h. When the boat is traveling with the current, the effective speed is 20 km/h, and when it is traveling against the current, the effective speed is 16 km/h. This explains why it takes less time to cover the distance with the current compared to against the current.

Please let me know if you need any further clarification.