Question

Мальчик треть времени всего движения ехал на велосипеде со скоростью 13 км/ч, а оставшийся участок шёл пешком со скоростью 4 км/ч. Какова его средняя скорость на всём пути? Ответ выразить в км/ч, округлив до целых.

Answer 1

Не знаю как до целых 6.5 км/ч,то ли просто 6,то ли 7

Answer 2

Problem Analysis

A boy spends a third of his total travel time riding a bicycle at a speed of 13 km/h, and the remaining distance he walks at a speed of 4 km/h. We need to calculate his average speed for the entire journey.

Solution

To find the average speed, we can use the formula:

Average Speed = Total Distance / Total Time

Let's assume the total distance is D km and the total time is T hours.

The time spent riding the bicycle can be calculated as: Time1 = (1/3) * T

The time spent walking can be calculated as: Time2 = (2/3) * T

The distance traveled while riding the bicycle can be calculated as: Distance1 = Speed1 * Time1

The distance traveled while walking can be calculated as: Distance2 = Speed2 * Time2

The total distance is the sum of the distances traveled while riding the bicycle and walking: Total Distance = Distance1 + Distance2

The total time is the sum of the time spent riding the bicycle and walking: Total Time = Time1 + Time2

Finally, we can calculate the average speed using the formula: Average Speed = Total Distance / Total Time

Let's substitute the given values into the formulas and calculate the average speed.

Calculation

Given: - Speed1 (riding the bicycle) = 13 km/h - Speed2 (walking) = 4 km/h

We need to calculate the average speed.

Using the formulas mentioned above, we can calculate the average speed as follows:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = Speed1 * Time1

Distance2 = Speed2 * Time2

Total Distance = Distance1 + Distance2

Total Time = Time1 + Time2

Average Speed = Total Distance / Total Time

Substituting the given values:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = 13 * Time1

Distance2 = 4 * Time2

Total Distance = Distance1 + Distance2

Total Time = Time1 + Time2

Average Speed = Total Distance / Total Time

Simplifying the equations:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = 13 * (1/3) * T

Distance2 = 4 * (2/3) * T

Total Distance = (13 * (1/3) * T) + (4 * (2/3) * T)

Total Time = (1/3) * T + (2/3) * T

Average Speed = Total Distance / Total Time

Simplifying further:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = (13/3) * T

Distance2 = (8/3) * T

Total Distance = (13/3) * T + (8/3) * T

Total Time = (3/3) * T

Average Speed = Total Distance / Total Time

Simplifying the equations:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = (13/3) * T

Distance2 = (8/3) * T

Total Distance = (21/3) * T

Total Time = T

Average Speed = Total Distance / Total Time

Simplifying further:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = (13/3) * T

Distance2 = (8/3) * T

Total Distance = (21/3) * T

Total Time = T

Average Speed = (21/3) * T / T

Simplifying the equations:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = (13/3) * T

Distance2 = (8/3) * T

Total Distance = (21/3) * T

Total Time = T

Average Speed = (21/3) * T / T

Simplifying further:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = (13/3) * T

Distance2 = (8/3) * T

Total Distance = (21/3) * T

Total Time = T

Average Speed = 21/3

Simplifying the equations:

Time1 = (1/3) * T

Time2 = (2/3) * T

Distance1 = (13/3) * T

Distance2 = (8/3) * T

Total Distance = (21/3) * T

Total Time = T

Average Speed = 7

Therefore, the boy's average speed for the entire journey is 7 km/h.

Answer

The boy's average speed for the entire journey is 7 km/h.