Question

Из Москвы и Санкт-Петербурга навстречу друг другу вышли одновременно два поезда.Скорость первого поезда 45 км в час а скорость второго поезда 35 км в час.Какое расстояние будет между поездами через 5 часов после отправления если расстояние от Москвы до Санкт-Петербурга равно 640 км? решить двумя способами!!!

Answer 1

1 способ
1) 45+35=80 км в час - скорость
2) 640-(80*5)=640-400=240 км
2 вариант
1) 45*5=225 км - проедет 1 поезд
2) 35*5=175 км - проедет 2 поезд
3) 640-(225+175)=240 км
ответ: 240 км

Answer 2

Problem Statement

Two trains depart simultaneously from Moscow and St. Petersburg towards each other. The first train has a speed of 45 km/h, while the second train has a speed of 35 km/h. The distance between Moscow and St. Petersburg is 640 km. We need to find the distance between the trains after 5 hours of departure using two different methods.

Method 1: Distance = Speed x Time

To find the distance between the trains after 5 hours, we can use the formula Distance = Speed x Time.

For the first train: - Speed = 45 km/h - Time = 5 hours

Using the formula, we can calculate the distance traveled by the first train: Distance1 = Speed1 x Time = 45 km/h x 5 hours = 225 km

For the second train: - Speed = 35 km/h - Time = 5 hours

Using the formula, we can calculate the distance traveled by the second train: Distance2 = Speed2 x Time = 35 km/h x 5 hours = 175 km

The total distance between the trains after 5 hours can be calculated by adding the distances traveled by each train: Total Distance = Distance1 + Distance2 = 225 km + 175 km = 400 km

Therefore, the distance between the trains after 5 hours of departure is 400 km.

Method 2: Relative Speed x Time

Another way to find the distance between the trains after 5 hours is by using the concept of relative speed. The relative speed is the difference between the speeds of the two trains.

Relative Speed = Speed1 - Speed2 = 45 km/h - 35 km/h = 10 km/h

Using the formula Distance = Speed x Time, we can calculate the distance traveled by the trains relative to each other: Distance = Relative Speed x Time = 10 km/h x 5 hours = 50 km

Since the trains are moving towards each other, the distance between them is decreasing. Therefore, the distance between the trains after 5 hours is the initial distance minus the distance traveled relative to each other: Distance between the trains = Initial Distance - Distance = 640 km - 50 km = 590 km

Therefore, the distance between the trains after 5 hours of departure is 590 km.

Conclusion

The distance between the trains after 5 hours of departure can be calculated using two different methods. According to the first method, the distance is 400 km, while according to the second method, the distance is 590 km.