Question

Расстояние между двумя городами 270 км. Из них одновременно в одном направлении выехали две машины. Первая машины ехала со скоростью 90 км/ч, а вторая машина ехала со скоростью 75 км/ч и отставала от первой сколько часов они были в пути, если в конце пути расстояние между ними стало 315км?

Answer 1

Ответ:  3 часа.

Пошаговое объяснение:

Решение.

Разность скоростей v=90-75 = 15 км/час.

Разность в расстоянии s=315-270 = 45 км.

s=vt;  45=15t;

15t=45;

t=3 часа.

Answer 2

Problem Analysis

We are given that the distance between two cities is 270 km. Two cars start simultaneously from these cities in the same direction. The first car travels at a speed of 90 km/h, while the second car travels at a speed of 75 km/h and falls behind the first car. We need to determine how many hours they were on the road if, at the end of the journey, the distance between them became 315 km.

Solution

Let's denote the time they were on the road as t (in hours). We can use the formula distance = speed × time to calculate the distance traveled by each car.

The distance traveled by the first car is given by distance1 = speed1 × t.

The distance traveled by the second car is given by distance2 = speed2 × t.

We are given that the distance between the two cars at the end of the journey is 315 km. Therefore, we can write the equation distance1 - distance2 = 315.

Substituting the expressions for distance1 and distance2, we get speed1 × t - speed2 × t = 315.

Simplifying the equation, we have (speed1 - speed2) × t = 315.

We can now solve this equation to find the value of t.

Calculation

Let's substitute the given values into the equation and solve for t.

speed1 = 90 km/h speed2 = 75 km/h

(speed1 - speed2) × t = 315

(90 - 75) × t = 315

15 × t = 315

t = 315 / 15

t = 21

Therefore, they were on the road for 21 hours.

Answer

The two cars were on the road for 21 hours before the distance between them became 315 km.