Question

Скорость лодки по течению реки 9км/ч,скорость течения реки 3 км/ч. Сколько времени понадобится, чтобы на этой лодке проплыть 27 км по реке и вернуться обратно?

Answer 1

Собственная скорость лодки 9-3=6 км/ч
Тогда ее скорость против течения 6-3=3 км/ч.
Получаем
(27:9)+(27:3)=3+9=12 часов

Answer 2

Calculation of Time Required to Travel 27 km by Boat

To calculate the time required to travel 27 km by boat along a river with a current, we need to consider the speed of the boat and the speed of the current.

Given: - Speed of the boat in still water: 9 km/h - Speed of the river current: 3 km/h

To calculate the time required to travel a certain distance, we can use the formula:

Time = Distance / Speed

Let's calculate the time required to travel 27 km downstream (along the current) and then return upstream (against the current).

Downstream Journey

When traveling downstream, the speed of the boat is increased by the speed of the current. Therefore, the effective speed of the boat is:

Effective Speed Downstream = Speed of the Boat + Speed of the Current

Substituting the given values:

Effective Speed Downstream = 9 km/h + 3 km/h = 12 km/h

Now, we can calculate the time required to travel 27 km downstream:

Time Downstream = Distance / Effective Speed Downstream

Substituting the values:

Time Downstream = 27 km / 12 km/h = 2.25 hours

Upstream Journey

When traveling upstream, the speed of the boat is decreased by the speed of the current. Therefore, the effective speed of the boat is:

Effective Speed Upstream = Speed of the Boat - Speed of the Current

Substituting the given values:

Effective Speed Upstream = 9 km/h - 3 km/h = 6 km/h

Now, we can calculate the time required to travel 27 km upstream:

Time Upstream = Distance / Effective Speed Upstream

Substituting the values:

Time Upstream = 27 km / 6 km/h = 4.5 hours

Total Time Required

To calculate the total time required for the round trip, we add the time for the downstream journey and the time for the upstream journey:

Total Time = Time Downstream + Time Upstream

Substituting the values:

Total Time = 2.25 hours + 4.5 hours = 6.75 hours

Therefore, it will take approximately 6.75 hours to travel 27 km by boat along the river and return back.

Please note that these calculations assume a constant speed throughout the journey and do not take into account any other factors that may affect the actual travel time.