Question

Помогите пожалуйста!!!Танк проехал по грунтовой дороге со скоростью 30 км / ч, затратив две трети всего времени. Последнюю треть времени он проехал по шоссе со скоростью 60 км / ч. Какова средняя скорость движения танка?

Answer 1

V=S/t
S1=V1*2*t/3     S2=V2*t/3
V=(V1*2*t/3 +V2*t/3)\t=t*(2*V1+V2)/3*t=2*V1+V2/3=2*30+60/3=40 км/ч

Answer 2

Танк проехал по грунтовой дороге со скоростью 30 км / ч, затратив две трети всего времени. Последнюю треть времени он проехал по шоссе со скоростью 60 км / ч. Какова средняя скорость движения танка?

Дано V1=30 км/ч  V2=2*V1=60 км/ч
t1=2*t/3   t2=1*t/3
Vcр-?

Vср=S/t=(S1+S2)/t=(V1*2*t/3   +2*V1*t/3)/t=4*V1/3=4*30/3=40 км/ч

Ответ Vср=40 км/ч

Answer 3

Calculation of Average Speed

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

Let's assume that the tank traveled a distance of D kilometers. According to the given information, the tank spent two-thirds of the total time traveling at a speed of 30 km/h on a dirt road, and the remaining one-third of the time traveling at a speed of 60 km/h on a highway.

The time spent on the dirt road can be calculated as (2/3) * T, where T is the total time taken. Similarly, the time spent on the highway can be calculated as (1/3) * T.

The distance traveled on the dirt road can be calculated as (2/3) * D, and the distance traveled on the highway can be calculated as (1/3) * D.

To find the average speed, we divide the total distance traveled by the total time taken:

Average Speed = Total Distance / Total Time

Let's calculate the average speed using the given information.

Calculation Steps:

1. Let's assume the total time taken as T hours. 2. The time spent on the dirt road is (2/3) * T hours. 3. The time spent on the highway is (1/3) * T hours. 4. The distance traveled on the dirt road is (2/3) * D kilometers. 5. The distance traveled on the highway is (1/3) * D kilometers. 6. The total distance traveled is D kilometers. 7. The average speed is Total Distance / Total Time.

Calculation:

Let's calculate the average speed using the given information:

Given: - Speed on the dirt road = 30 km/h - Speed on the highway = 60 km/h

Assuming the total distance traveled as D kilometers.

The time spent on the dirt road is (2/3) * T hours, and the time spent on the highway is (1/3) * T hours.

The distance traveled on the dirt road is (2/3) * D kilometers, and the distance traveled on the highway is (1/3) * D kilometers.

The total distance traveled is D kilometers.

The average speed is Total Distance / Total Time.

Let's calculate the average speed:

Average Speed = (Distance on Dirt Road + Distance on Highway) / (Time on Dirt Road + Time on Highway)

Average Speed = ((2/3) * D + (1/3) * D) / ((2/3) * T + (1/3) * T)

Simplifying the equation:

Average Speed = (3/3) * D / (3/3) * T

Average Speed = D / T

Therefore, the average speed of the tank is D / T km/h.

Please provide the value of the total distance traveled (D) or the total time taken (T) so that we can calculate the average speed accurately.