Question

Колонна пионеров движется со скоростью 9 км/ч, растянувшись по дороге на 750 м. Из головы колонны в хвост отправляется велосипедист, скорость которого 18 км/ч. Через какое время он достигнет головной машины и вернется обратно.

Answer 1

0,750 / (9+27) =(0,750 / 36)час = 0,750*3600/36 = 75 с или 1 минута 15 секунд

Answer 2

Problem Analysis

We are given that a column of pioneers is moving at a speed of 9 km/h, stretched along a road for a distance of 750 m. A cyclist leaves the head of the column and rides towards the tail at a speed of 18 km/h. We need to determine the time it takes for the cyclist to reach the head of the column and return back.

Solution

To solve this problem, we can calculate the time it takes for the cyclist to reach the head of the column and then double that time to account for the return trip.

Let's calculate the time it takes for the cyclist to reach the head of the column:

1. Convert the speed of the cyclist from km/h to m/s: - Speed of the cyclist = 18 km/h = 18 * (1000/3600) m/s = 5 m/s.

2. Calculate the time it takes for the cyclist to reach the head of the column: - Distance = 750 m. - Speed = 5 m/s. - Time = Distance / Speed = 750 m / 5 m/s = 150 s.

Now, we need to double the time to account for the return trip:

3. Double the time to account for the return trip: - Total time = 2 * 150 s = 300 s.

Therefore, it will take the cyclist 300 seconds to reach the head of the column and return back.

Answer: The cyclist will reach the head of the column and return back in 300 seconds.