Question

Из двух городов А и В, расстояние между которыми 390 км, навстречу друг другу одновременно выехали два автомобиля. Скорость автомобиля выехавшего из А, равна 60 км/ч, из В - 70 км/ч. Через сколько часов после встречи автомобиль, выехавший из А, прибудет в В?

Answer 1

1) 60+70=130(км/час)   скорость сближения
2) 390 : 130 = 3(ч) через 3 часа они встретятся
3) 60 * 3 = 180(км) проедет автомобиль из А до встречи
4) 390-180=210(км) осталось проехать автомобилю из А до В
5) 210 : 60 = 3,5(ч) через 3,5 часа после встречи автомобиль, выехавший из А, прибудет в В

Answer 2

Problem Analysis

We have two cities, A and B, with a distance of 390 km between them. Two cars start simultaneously from each city and travel towards each other. The speed of the car starting from city A is 60 km/h, and the speed of the car starting from city B is 70 km/h. We need to determine how many hours it will take for the car starting from city A to reach city B after they meet.

Solution

To solve this problem, we can use the formula:

Time = Distance / Speed

Let's calculate the time it takes for the two cars to meet:

The total distance between the two cities is 390 km. When the two cars meet, they would have traveled a combined distance of 390 km. Therefore, the distance traveled by the car starting from city A can be calculated as:

Distance traveled by car A = (Speed of car A) x (Time taken to meet)

Similarly, the distance traveled by the car starting from city B can be calculated as:

Distance traveled by car B = (Speed of car B) x (Time taken to meet)

Since the total distance traveled by both cars is equal to the distance between the two cities (390 km), we can write the equation:

(Speed of car A) x (Time taken to meet) + (Speed of car B) x (Time taken to meet) = 390

Simplifying the equation, we get:

(Speed of car A + Speed of car B) x (Time taken to meet) = 390

Now, we can substitute the given values:

(60 km/h + 70 km/h) x (Time taken to meet) = 390

Simplifying further:

130 km/h x (Time taken to meet) = 390

Dividing both sides of the equation by 130 km/h:

Time taken to meet = 390 km / 130 km/h

Calculating the result:

Time taken to meet = 3 hours

Therefore, it will take 3 hours for the car starting from city A to reach city B after they meet.

Answer

The car starting from city A will reach city B 3 hours after they meet.