Question

Расстояние между двумя пристанями 8 км.По течению теплоход двигался со скоростью 15 км/час,а против течения-со скоростью 10 км/час. С какой средней скоростью теплоход прошел весь путь туда и обратно?

Answer 1

Средняя скорость это весь пройденный путь делённый на все время в пути. Теплоход двигался между пристанями в одну и в другую стороны, следовательно S= 8×2=16км. Теперь найдём время. Чтобы найти время нужнорасстояние разделить на скорость. t по течению: 8/15 часа; t против течения: 8/10 часа. Теперь найдём общее время: 8/15+8/10= 4/3 часа. Найдём среднюю скорость: 16:4/3= 12 км/ч

Answer 2

Calculation of Average Speed

To calculate the average speed of the boat for the entire round trip, we need to consider the speed of the boat both with and against the current.

Given: - Distance between the two piers: 8 km - Speed of the boat with the current: 15 km/h - Speed of the boat against the current: 10 km/h

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

Average Speed = (Total Distance)/(Total Time)

Since the boat is traveling to one pier and then returning to the other, the total distance covered is twice the distance between the piers, which is 8 km * 2 = 16 km.

To find the total time, we need to calculate the time taken for each leg of the journey.

Time taken to travel with the current:

The time taken to travel with the current can be calculated using the formula:

Time = Distance/Speed

Substituting the values, we get:

Time with current = 8 km / 15 km/h = 0.533 hours

Time taken to travel against the current:

Similarly, the time taken to travel against the current can be calculated using the formula:

Time = Distance/Speed

Substituting the values, we get:

Time against current = 8 km / 10 km/h = 0.8 hours

Total time for the round trip:

To find the total time for the round trip, we add the time taken to travel with the current and the time taken to travel against the current:

Total time = Time with current + Time against current = 0.533 hours + 0.8 hours = 1.333 hours

Average speed:

Finally, we can calculate the average speed using the formula:

Average Speed = Total Distance / Total Time = 16 km / 1.333 hours = 12 km/h

Therefore, the average speed of the boat for the entire round trip is 12 km/h.