Question

А Школьник живет в доме, стоящем около дороги между остановками A и B на расстоянии 800 м от A. В направлении от A к B по дороге каждый день проезжает автобус со скоростью 40 км/ч. На остановку B он приезжает в 8 часов утра. Минимально за сколько минут до 8 часов утра должен выйти из дома школьник, чтобы успеть уехать на автобусе? Школьник ходит со скоростью 4.8 км/ч, расстояние между остановками 2 км. Время, которое автобус стоит на остановке, очень мало. Ответом является целое число, в случае необходимости округлите до целых.

Answer 1

1) 2000м - 800м / 4,8 км/ч(80м/м) = 15 минут до 8.00 до остановки В
2) 2 км/ 40км/ч = 3 мин раньше
3) 800м / 80м/м + 3 мин = 13 мин до 8.00 от остановки А
ответ за 13 минут

Answer 2

Problem Analysis

To solve this problem, we need to determine the minimum number of minutes the student should leave their house before 8:00 am in order to catch the bus. We are given the following information: - The student's house is located 800 meters away from stop A. - The bus travels at a speed of 40 km/h from stop A to stop B. - The distance between stops A and B is 2 km. - The bus arrives at stop B at 8:00 am. - The student walks at a speed of 4.8 km/h.

Solution

To find the minimum number of minutes the student should leave their house before 8:00 am, we need to calculate the time it takes for the student to walk from their house to stop A and the time it takes for the bus to travel from stop A to stop B.

Let's calculate the time it takes for the student to walk from their house to stop A: - Distance from the student's house to stop A: 800 meters - Walking speed of the student: 4.8 km/h

To convert the student's walking speed to meters per minute, we can use the following conversion: - 1 km/h = 1000 meters / 60 minutes = 16.67 meters/minute

Therefore, the student's walking speed in meters per minute is: - 4.8 km/h * 1000 meters / 60 minutes = 80 meters/minute

To calculate the time it takes for the student to walk from their house to stop A, we can divide the distance by the walking speed: - Time = Distance / Speed - Time = 800 meters / 80 meters/minute = 10 minutes

Next, let's calculate the time it takes for the bus to travel from stop A to stop B: - Distance from stop A to stop B: 2 km - Bus speed: 40 km/h

To convert the bus speed to meters per minute, we can use the same conversion as before: - Bus speed in meters per minute = 40 km/h * 1000 meters / 60 minutes = 666.67 meters/minute

To calculate the time it takes for the bus to travel from stop A to stop B, we can divide the distance by the bus speed: - Time = Distance / Speed - Time = 2000 meters / 666.67 meters/minute = 3 minutes

Finally, we need to subtract the time it takes for the bus to travel from stop A to stop B from the time the bus arrives at stop B (8:00 am) to find the minimum number of minutes the student should leave their house before 8:00 am: - Time to leave = Time at stop B - Time for bus travel - Time to leave = 8:00 am - 3 minutes = 7:57 am

Therefore, the student should leave their house at 7:57 am in order to catch the bus.

Answer

The student should leave their house 3 minutes before 8:00 am in order to catch the bus.