Question

между пристанями по реке 40 километров Моторная лодка прошла этот путь по течению реки за 2 часа против течения реки за 4 часа Какова скорость течения реки

Answer 1

10 км ч скорость течения реки.

Answer 2

S-40км
по теч-2ч
прот теч-4ч
Решение
1)Vпо теч=S/tпо теч=40/2=20км-ч-по теч
2)40/4=10км/ч-прот теч
3)20-10=10км/ч-V теч

Answer 3

Calculation of River Current Speed

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

Speed of the boat in still water = Distance / Time

Let's calculate the speed of the boat in still water using the given information:

- Distance between the docks: 40 kilometers - Time taken to travel downstream (with the current): 2 hours - Time taken to travel upstream (against the current): 4 hours

To find the speed of the river current, we need to find the speed of the boat in still water. Let's assume the speed of the boat in still water is x and the speed of the river current is y.

When the boat is traveling downstream, the effective speed is the sum of the boat's speed in still water and the speed of the river current. So, the effective speed is x + y.

When the boat is traveling upstream, the effective speed is the difference between the boat's speed in still water and the speed of the river current. So, the effective speed is x - y.

Using the formula mentioned above, we can set up the following equations:

1. When traveling downstream: 40 = (x + y) * 22. When traveling upstream: 40 = (x - y) * 4 Let's solve these equations to find the values of x and y.

Solving the Equations

We can solve the equations by substituting the values and simplifying:

1. When traveling downstream: 40 = (x + y) * 2 - Simplifying: 2x + 2y = 40 - Dividing by 2: x + y = 20

2. When traveling upstream: 40 = (x - y) * 4 - Simplifying: 4x - 4y = 40 - Dividing by 4: x - y = 10

Now, we have a system of equations:

- Equation 1: x + y = 20 - Equation 2: x - y = 10

We can solve this system of equations using the method of substitution or elimination.

Let's use the method of elimination to solve the system of equations:

Adding Equation 1 and Equation 2, we get:

(x + y) + (x - y) = 20 + 10 - Simplifying: 2x = 30 - Dividing by 2: x = 15

Substituting the value of x into Equation 1, we get:

15 + y = 20 - Subtracting 15 from both sides: y = 5

Answer

Therefore, the speed of the boat in still water is 15 kilometers per hour and the speed of the river current is 5 kilometers per hour.

Please note that these calculations are based on the given information and assumptions made.