Question

15' 212. Поезд проходит расстояние между городами за 9 ч. Если он уве- личит скорость на 20 км/ч, то пройдет расстояние за 7 ч. Найдите ско- рость поезда и расстояние между городами.

Answer 1

Ответ:

630км

Объяснение:

x-скорость поезда, y-расстояние. Составим уравнение:

9x = y

7(x + 20) = y

7x + 140 = 9x

2x = 140

x = 70

y = 70 * 9 = 630км

Answer 2

Problem Analysis

We are given that a train travels a certain distance between two cities in 9 hours. If the train increases its speed by 20 km/h, it can cover the same distance in 7 hours. We need to find the speed of the train and the distance between the cities.

Solution

Let's assume the initial speed of the train is x km/h, and the distance between the cities is d km.

According to the given information, we can set up the following equations:

Equation 1: The train travels the distance in 9 hours at speed x km/h. Equation 2: The train travels the same distance in 7 hours at speed x + 20 km/h.

To find the speed of the train, we can solve these equations simultaneously.

Calculation

Let's solve the equations:

Equation 1: d = x * 9 (1) Equation 2: d = (x + 20) * 7 (2)

To find the value of x, we can equate equations (1) and (2):

x * 9 = (x + 20) * 7

Simplifying the equation:

9x = 7x + 140

2x = 140

x = 70

Now that we have the value of x, we can substitute it back into equation (1) to find the distance d:

d = 70 * 9

d = 630 km

Answer

The speed of the train is 70 km/h, and the distance between the cities is 630 km.

Please note that the information provided above is based on the given problem statement and the calculations made.