Question

ДАЮ 100 БАЛІВ! Мотоцикліст проїхав із пункту А до пункту Б з середньою швидкістю 30 км/год, а потім повернувся назад. З якою середньою швидкістю він повертався, якщо середня швидкість на всьому шляху становила 35 км/год. Я знаю відповідь - 42 км/год, але мені потрібне повне розв'язання до цієї задачі!

Answer 1

Ответ:

Пошаговое объяснение:

на скрине

Answer 2

Problem Analysis

In this problem, we are given that a motorcyclist traveled from point A to point B with an average speed of 30 km/h. Then, the motorcyclist returned back from point B to point A. We need to find the average speed at which the motorcyclist returned, given that the average speed for the entire journey was 35 km/h.

Solution

Let's assume the distance between point A and point B is d kilometers.

To find the average speed at which the motorcyclist returned, we can use the formula:

Average Speed = Total Distance / Total Time

We know that the average speed for the entire journey was 35 km/h. Therefore, the total distance traveled in the entire journey is 2d kilometers (since the motorcyclist traveled from A to B and then back from B to A).

We can calculate the total time taken for the entire journey using the formula:

Total Time = Total Distance / Average Speed

Substituting the values, we get:

Total Time = 2d / 35

Now, let's calculate the time taken for the first part of the journey (from A to B). We know that the average speed for this part was 30 km/h. Therefore, the time taken for this part is:

Time taken for first part = d / 30

Since the motorcyclist returned back from B to A, the time taken for the return journey will be the same as the time taken for the first part.

Therefore, the total time taken for the entire journey is:

Total Time = Time taken for first part + Time taken for return journey = d / 30 + d / 30 = 2d / 30

Now, we can equate the two expressions for the total time:

2d / 35 = 2d / 30

To find the average speed at which the motorcyclist returned, we can solve this equation for d.

Calculation

Let's solve the equation:

2d / 35 = 2d / 30

Multiplying both sides by 35 * 30 to eliminate the denominators:

60d = 70d

Subtracting 60d from both sides:

10d = 0

Dividing both sides by 10:

d = 0

Answer

The solution to the equation is d = 0. This means that the distance between point A and point B is 0 kilometers.

Since the distance is 0, it implies that the motorcyclist did not actually travel from point A to point B and back. Therefore, it is not possible to determine the average speed at which the motorcyclist returned.

Hence, the answer to the problem is that it is not possible to determine the average speed at which the motorcyclist returned.

I hope this helps! Let me know if you have any further questions.