Question

Расстояние между городами ровно 490 км.Из этих городов навстречу друг другу одновременно вышли два поезда и встретились через 3,5 часа.Определите скорость первого поезда,если известно,что она меньше скорости второго поезда на 10 км/ч.

Answer 1

1) 490 : 3,5 = 140 ( км/час ) скорость сближения поездов
2) ( 140 - 10 ) : 2 = 65 ( км/час ) скорость первого
Ответ 65 км/час

Answer 2

1)490/3,5=140(км/ч) - скорость обоих поездов
2)(140-10)÷2=65(км/ч) - скорость первого
Ответ:65 км/ч.

Answer 3

Problem Analysis

We are given that two trains start simultaneously from two cities and meet each other after 3.5 hours. The distance between the cities is 490 km, and we need to determine the speed of the first train, knowing that it is 10 km/h slower than the second train.

Solution

Let's assume the speed of the first train is x km/h. Since the second train is 10 km/h faster, its speed will be (x + 10) km/h.

We can use the formula distance = speed × time to calculate the distance traveled by each train.

The first train travels for 3.5 hours at a speed of x km/h, so the distance it covers is 3.5x km.

The second train also travels for 3.5 hours, but at a speed of (x + 10) km/h, so the distance it covers is 3.5(x + 10) km.

Since the total distance between the cities is 490 km, the sum of the distances covered by both trains should be equal to 490 km:

3.5x + 3.5(x + 10) = 490

Simplifying the equation:

3.5x + 3.5x + 35 = 490

7x + 35 = 490

Subtracting 35 from both sides:

7x = 455

Dividing both sides by 7:

x = 65

Therefore, the speed of the first train is 65 km/h.

Answer

The speed of the first train is 65 km/h.