Question

Автомобиль 2 часа ехал со скоростью 90 км /ч и 3 ч со скоростью 70 км/ч .Какова средняя скорость автомобиля ? а)80 б)85 с)78

Answer 1

1)90*2=180(км)-проехал за 2 часа
2)70*3=210(км)-проехал за 3 часа
3)2+3=5(час)-был в пути
4)180+210=390(км)-проехал всего
5)390:5=78(км/час)-средняя скорость
Ответ: вариант С-78 км/час

Answer 2

Calculation of Average Speed

To calculate the average speed of the car, we need to find the total distance traveled and the total time taken.

Given: - The car traveled for 2 hours at a speed of 90 km/h. - The car traveled for 3 hours at a speed of 70 km/h.

To find the total distance, we can add the distances traveled at each speed: - Distance traveled at 90 km/h = 90 km/h * 2 hours = 180 km - Distance traveled at 70 km/h = 70 km/h * 3 hours = 210 km

The total distance traveled is 180 km + 210 km = 390 km.

To find the total time taken, we can add the times taken at each speed: - Time taken at 90 km/h = 2 hours - Time taken at 70 km/h = 3 hours

The total time taken is 2 hours + 3 hours = 5 hours.

Now, we can calculate the average speed using the formula:

Average Speed = Total Distance / Total Time

Substituting the values, we get:

Average Speed = 390 km / 5 hours = 78 km/h

Therefore, the average speed of the car is 78 km/h (option c).