Question

На путь по теченю моторная лодка затратила 3 часа.Найдите сколько времени (часов) потребуется на обратный путь,если скорость течения реки 2км\ч а скорость лодки в стоячей воде v(км\ч) найдите t при а)v=14 km\ч b)v=10 км\ч4

Answer 1

1)14+2=16(км/ч)- по течению
2)16*3=48(км)- расстояние
3)14-2=12(км/ч)- против течения
4)48:12=4(ч)
ответ:4часа

Answer 2

Calculation of Time for the Return Journey

To calculate the time required for the return journey, we need to consider the speed of the current and the speed of the boat in still water.

Let's denote the speed of the current as v_c (2 km/h) and the speed of the boat in still water as v (km/h).

The time taken for the forward journey is given as 3 hours.

To calculate the time for the return journey, we can use the formula:

Time = Distance / Speed

Since the distance for the forward and return journeys is the same, we can assume it as d km.

For the forward journey, the effective speed of the boat is the difference between the speed of the boat in still water and the speed of the current:

Effective Speed for Forward Journey = v - v_c

Using the formula, we can calculate the distance for the forward journey:

Distance for Forward Journey = (v - v_c) * 3

For the return journey, the effective speed of the boat is the sum of the speed of the boat in still water and the speed of the current:

Effective Speed for Return Journey = v + v_c

Using the formula, we can calculate the time for the return journey:

Time for Return Journey = d / (v + v_c)

Now, let's substitute the given values and calculate the time for the return journey for two different boat speeds:

a) When v = 14 km/h: - Distance for Forward Journey = (14 - 2) * 3 = 36 km - Time for Return Journey = 36 / (14 + 2) = 36 / 16 = 2.25 hours

b) When v = 10 km/h: - Distance for Forward Journey = (10 - 2) * 3 = 24 km - Time for Return Journey = 24 / (10 + 2) = 24 / 12 = 2 hours

Therefore, the time required for the return journey is: a) When v = 14 km/h: 2.25 hours b) When v = 10 km/h: 2 hours

Please note that the given question does not provide the value of d (distance), so we cannot calculate the exact time for the return journey. However, we can calculate the time based on the given boat speeds.