Question

катер проплыл 30 км по течению реки за 1,5 часа и вернулся на туже пристань потратив на обратный путь 2 часа найдите собственную скорость катера и скорость течения реки Помогите пожалуйста!! алгебра 7 класс без километра не нужной фигни!!​

Answer 1

Ответ:

30:1.5=20

20•2=40

відповідь 40 км в час

Answer 2

Problem Analysis

We are given that a boat traveled 30 km downstream in 1.5 hours and returned to the same dock in 2 hours. We need to find the speed of the boat and the speed of the river's current.

Let's assume the speed of the boat is represented by b and the speed of the river's current is represented by c.

Downstream Journey

During the downstream journey, the boat is moving in the same direction as the river's current. Therefore, the effective speed of the boat will be the sum of its own speed and the speed of the river's current.

The time taken for the downstream journey is given as 1.5 hours, and the distance traveled is 30 km. We can use the formula:

Distance = Speed × Time

Substituting the values, we have:

30 = (b + c) × 1.5

Upstream Journey

During the upstream journey, the boat is moving against the direction of the river's current. Therefore, the effective speed of the boat will be the difference between its own speed and the speed of the river's current.

The time taken for the upstream journey is given as 2 hours, and the distance traveled is also 30 km. We can use the same formula:

Distance = Speed × Time

Substituting the values, we have:

30 = (b - c) × 2

Solving the Equations

We now have a system of two equations with two variables. We can solve this system to find the values of b and c.

Let's solve the equations using the substitution method.

From equation we can express b in terms of c:

b = 30/1.5 - c = 20 - c [[3]]

Substituting this value of b in equation we have:

30 = (20 - c - c) × 2

Simplifying the equation:

30 = (20 - 2c) × 2

30 = 40 - 4c

4c = 40 - 30

4c = 10

c = 10/4

c = 2.5

Now, substituting the value of c back into equation [[3]], we can find b:

b = 20 - 2.5

b = 17.5

Therefore, the speed of the boat is 17.5 km/h and the speed of the river's current is 2.5 km/h.

Answer

The speed of the boat is 17.5 km/h and the speed of the river's current is 2.5 km/h.

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