Question

Велосипедист, проехав 4 км со скоростью 12 км/ч, остановился и отдыхал в течение 40 мин. Оставшиеся 8 км пути он проехал со скоростью 8 км/ч. Найдите среднюю скорость (в км/ч) велосипедиста.

Answer 1

4/12=1/3 ч = 20 мин
8/8=1 ч
20мин+40мин+1ч=2ч
4+8=12 км
12/2=6км/ч
Ответ:6 км/ч

Answer 2

Calculation of Average Speed

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

Average Speed = Total Distance / Total Time

Let's calculate the average speed step by step.

1. The cyclist traveled 4 km with a speed of 12 km/h. We can calculate the time taken for this part of the journey using the formula:

Time = Distance / Speed

For the first part of the journey: Time = 4 km / 12 km/h = 1/3 hour

2. The cyclist then rested for 40 minutes, which is equal to 40/60 = 2/3 hour.

3. After resting, the cyclist traveled the remaining 8 km with a speed of 8 km/h. We can calculate the time taken for this part of the journey using the same formula:

Time = 8 km / 8 km/h = 1 hour

4. Now, let's calculate the total distance and total time:

Total Distance = 4 km + 8 km = 12 km Total Time = 1/3 hour + 2/3 hour + 1 hour = 5/3 hour

5. Finally, we can calculate the average speed:

Average Speed = Total Distance / Total Time = 12 km / (5/3) hour = 7.2 km/h

Therefore, the average speed of the cyclist is 7.2 km/h.