Question

Из пункта А в пункт В с интервалом в 10 мин вышли два поезда со скоростью 60 км/ч. Какую скорость имел встречный поезд, если он повстречал эти поезда через 4 мин один после другого? А. 100 км/ч Б. 90 км/ч В. 40 км/ч Г. 35 км/ч.

Answer 1

Не знаю, откуда эти ответы, т.к. получается 90 км/ч
10мин=1/6ч
1/6*60=10 км расстояние между поездами
4 мин=1/15ч
10:1/15=150 км/ч скорость сближения между встречным и вторым поездом
150-60=90 км/ч скорость встречного поезда

Answer 2

Problem Analysis

We have two trains that leave point A with a 10-minute interval, both traveling at a speed of 60 km/h. We need to determine the speed of the oncoming train when it meets these trains after 4 minutes, one after the other.

Solution

To solve this problem, we can use the formula: speed = distance / time.

Let's calculate the distance traveled by the first train in 4 minutes: - The first train travels for 4 minutes at a speed of 60 km/h. - We can convert the time to hours by dividing it by 60: 4 minutes / 60 = 0.067 hours. - The distance traveled by the first train is then: distance = speed * time = 60 km/h * 0.067 hours = 4.02 km.

Now, let's calculate the distance traveled by the second train in 4 minutes: - The second train starts 10 minutes after the first train, so it travels for 4 minutes less. - The time traveled by the second train is: 4 minutes - 4 minutes = 0 minutes. - The distance traveled by the second train is then: distance = speed * time = 60 km/h * 0 hours = 0 km.

When the oncoming train meets the first train, it has traveled a distance of 4.02 km. When it meets the second train, it has traveled a distance of 0 km.

To find the speed of the oncoming train, we can use the formula: speed = distance / time. The time it takes for the oncoming train to meet both trains is the same, as they are meeting one after the other. Therefore, the time is 4 minutes.

Let's calculate the speed of the oncoming train: - The distance traveled by the oncoming train is the sum of the distances traveled by the first and second trains: 4.02 km + 0 km = 4.02 km. - The time taken is 4 minutes. - The speed of the oncoming train is then: speed = distance / time = 4.02 km / 4 minutes.

Now, let's convert the speed to km/h: - We can convert the time to hours by dividing it by 60: 4 minutes / 60 = 0.067 hours. - The speed of the oncoming train is then: speed = 4.02 km / 0.067 hours.

Calculating the speed: - speed = 4.02 km / 0.067 hours = 60 km/h.

Therefore, the speed of the oncoming train is 60 km/h.

Answer

The correct answer is 60 km/h (Option A).