Question

Помогите!! 5 класс.От пристани А вниз по течению реки отправился катер.В это же время от пристани В навстречу ему вышел второй катер с же собственной скоростью.Первый катер достиг пристани В через 4 часа.На каком расстоянии от пристани А был в это время второй катер,если скорость течения реки-2 км/ч?

Answer 1

Пусть собственная скорость катеров - х км/ч
Значит первый шел со скоростью х+2 км/ч
Второй со скоростью х-2 км/ч
Первый за 4 часа пройдет 4х+8 км
Второй 4х-8 км
Значит второй пройдет меньше на 
4х+8-(4х-8)=16 км
Значит второму катеру до пристани А останется 16 км

Answer 2

Problem Analysis

We are given that a boat departs from port A and travels downstream along a river. At the same time, another boat departs from port B and travels towards the first boat with its own speed. The first boat reaches port B in 4 hours. We need to find the distance between port A and the second boat at that time, given that the speed of the river current is 2 km/h.

Solution

Let's assume the speed of the first boat is x km/h. Since the first boat reaches port B in 4 hours, the distance between port A and port B can be calculated as 4x km.

Now, let's consider the second boat. Since it is traveling towards the first boat, its effective speed will be the difference between its own speed and the speed of the river current. Let's assume the speed of the second boat is y km/h. Therefore, the effective speed of the second boat is (y - 2) km/h.

Since both boats are traveling towards each other, the total distance covered by both boats is equal to the distance between port A and port B. Therefore, we can write the equation:

4x + 4(y - 2) = 4x + 4y - 8

Simplifying the equation, we get:

4y - 8 = 0

Solving for y, we find:

4y = 8

y = 2

Therefore, the speed of the second boat is 2 km/h.

To find the distance between port A and the second boat at that time, we need to calculate the distance covered by the second boat in 4 hours. Since the speed of the second boat is 2 km/h, the distance covered by the second boat is:

Distance = Speed × Time = 2 km/h × 4 h = 8 km

Therefore, the second boat is 8 km away from port A at that time.

Answer

The second boat is 8 km away from port A at that time.