Question

Автомобиль ехал 3 часа по шоссе и 2 часа по просе- лочной дороге, где его ско рость была на 15 км/ч меньше, чем на шоссе. Всего за 5 часов автомобиль проехал 270 км. Найдите скорость aфтомобиля на шоссе и на проселочной дороге.

Answer 1

T1=3, t2=2 v1=? v2=v1-15 s12=270
s12=(v1*t1)+(v2*t2)=(v1*3)+((v1-15)*2)
270=3v1+2v1-30=5v1-30
5v1=270+30=300
v1=300/5=60 (асфальт)
v2=v1-15=60-15=45 (просёлок)

Answer 2

Пусть х скорость по шоссе, тогда по проселочной х-15
3х+2(х-15)=270
3х+2х-30=270
3х+2х=270+30
5х=300
Х=60 км/ч скорость по шоссе
60-15= 45 км/ч скорость по проселочной

Answer 3

Problem Analysis

We are given that a car traveled for 3 hours on a highway and 2 hours on a dirt road. The speed of the car on the dirt road was 15 km/h less than on the highway. The total distance traveled by the car in 5 hours was 270 km. We need to find the speed of the car on the highway and on the dirt road.

Solution

Let's assume the speed of the car on the highway is x km/h. Since the speed on the dirt road is 15 km/h less, the speed on the dirt road would be x - 15 km/h.

We can use the formula distance = speed × time to calculate the distances traveled on the highway and the dirt road.

The distance traveled on the highway can be calculated as x km/h × 3 hours = 3x km.

The distance traveled on the dirt road can be calculated as (x - 15) km/h × 2 hours = 2(x - 15) km.

According to the problem, the total distance traveled is 270 km. So we can write the equation:

3x + 2(x - 15) = 270

Simplifying the equation:

3x + 2x - 30 = 270

5x - 30 = 270

5x = 300

x = 60

The speed of the car on the highway is 60 km/h.

To find the speed of the car on the dirt road, we substitute the value of x into the expression x - 15:

60 - 15 = 45

The speed of the car on the dirt road is 45 km/h.

Answer

The speed of the car on the highway is 60 km/h and the speed of the car on the dirt road is 45 km/h.