Question

Из пункта А в пункт В вышел товарный поезд.Спустя 3 часа вслед за ним вышел пассажирский поезд,скорость которого на 30 км/час больше скорости товарного.через 15 часов после своего выхода пассажирский поезд оказался впереди товарного на 300 км. найтиде скорость товарного поезда

Answer 1

Пусть х- скорость пассажирского поезда
тогда х-20 скорость товарного

3х- путь,пройденный пассажирским за 3ч

4(х-20)- путь,пройденный товарным за 4 ч

3х-4(х-20)=10

3х-4х+80=10

х=70 км/ч- скорость пассажирского

70-20=50 км/ч- скорость товарного

Ответ: 50 км/ч 

Answer 2

Problem Analysis

We are given that a freight train left point A and, after 3 hours, a passenger train left point A as well. The speed of the passenger train is 30 km/h faster than the speed of the freight train. After 15 hours from its departure, the passenger train was 300 km ahead of the freight train. We need to find the speed of the freight train.

Solution

Let's assume the speed of the freight train is x km/h. Since the speed of the passenger train is 30 km/h faster, its speed is x + 30 km/h.

We can use the formula distance = speed × time to calculate the distances traveled by both trains.

The freight train travels for 15 hours, so the distance it covers is 15x km.

The passenger train travels for 15 - 3 = 12 hours, so the distance it covers is 12(x + 30) km.

According to the problem, the passenger train is 300 km ahead of the freight train, so we can set up the equation:

12(x + 30) = 15x + 300

Now, let's solve this equation to find the value of x.

Calculation

Expanding the equation:

12x + 360 = 15x + 300

Rearranging the equation:

12x - 15x = 300 - 360

-3x = -60

Dividing both sides by -3:

x = 20

Answer

The speed of the freight train is 20 km/h.