Question

Между городами А и В, находящимися на расстоянии 20 км, курсирует автобус со скоростью 60 км/ч. Первоначально автобус выезжает из города А. В каждом городе у автобуса десятиминутная остановка. Однажды из города А одновременно с автобусом выехал велосипедист со скоростью 20 км/ч. Через какое время автобус впервые с момента выезда велосипедиста вернется в город А. Ответ выразите в минутах и запишите в таблицу ответов только числовое значение.

Answer 1

20/60= 1/3 (ч) = 20 мин - время автобуса от А до В
20 мин + 10 мин (остановка) + 20 мин = 50 мин

Answer 2

Problem Analysis

To solve this problem, we need to determine the time it takes for the bicycle to catch up with the bus. The bus travels at 60 km/h, while the cyclist travels at 20 km/h. The bus makes a 10-minute stop in each city.

Solution

Let's calculate the time it takes for the cyclist to catch up with the bus.

The relative speed of the cyclist with respect to the bus is the difference between their speeds, which is 60 km/h - 20 km/h = 40 km/h.

The distance between the cities is 20 km, and the bus travels at 60 km/h. Therefore, the time it takes for the bus to travel from city A to city B is given by the formula: time = distance / speed = 20 km / 60 km/h = 1/3 hours = 20 minutes

Now, let's calculate the time it takes for the cyclist to catch up with the bus. The time it takes for the cyclist to catch up with the bus is given by the formula: time = distance / relative speed = 20 km / 40 km/h = 1/2 hours = 30 minutes

However, we need to consider the 10-minute stop in city B. Therefore, the total time it takes for the cyclist to catch up with the bus is 30 minutes + 10 minutes = 40 minutes.

Answer

The cyclist will catch up with the bus and return to city A after 40 minutes.